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Algebra II: Functions, Structure, and Modeling

Grade 11 · Christian · NGSS/CCSS-aligned

This is the algebra course that takes "graphing parabolas" from Algebra I and blows it out into six more families of functions, polynomials, rational expressions, radicals, exponentials/logs, trig, and finally sequences and statistics. The thread running through all eight units is one question asked over and over in new clothes: given an equation, what does the graph look like, and given a graph or a real situation, what's the equation? Your child will get a lot of practice moving between an equation, a graph, a table, and a word problem, for each of these families, and by the end they should be able to look at data or a situation and say "that's exponential, not linear" or "that needs a hole, not an asymptote" and explain why. It's a full year of building one increasingly large toolbox rather than eight unrelated topics.

What your child will learn

The whole year, in plain English. Tap any unit to see every skill inside, nothing is hidden.

Quadratic Functions Revisited: Structure and Complex Numberspeek inside ▸

This unit takes quadratics, which your child can already factor and graph from Algebra I, and gives them three ways to write the same equation (standard, factored, vertex), a way to predict how many solutions an equation has before solving it (the discriminant), and a brand-new kind of number for when the answer to a square root is negative. The big idea is that completing the square isn't a random trick, it's the one procedure that generates vertex form AND the quadratic formula, so understanding it once explains both.

  1. Completing the square as a rewriting procedure on x^2+bx+c

    Given a quadratic in standard form with a leading coefficient of 1, complete the square to rewrite it in vertex form.

  2. The discriminant as a predictor of root type

    Use the discriminant b^2-4ac to predict whether a quadratic has two real roots, one repeated real root, or two complex roots, before solving the equation.

  3. The derivation of the quadratic formula from completing the square

    Explain why completing the square on ax^2+bx+c derives the quadratic formula, connecting each step of the general derivation to the corresponding step in a numeric example.

  4. Representation choice among standard, factored, and vertex form of a quadratic

    Given a real-world scenario modeled by a quadratic (projectile height, rectangular area, revenue), decide which algebraic form of the quadratic (standard, factored, or vertex) to write before solving, and justify the choice by naming the graph feature the question asks for.

  5. Arithmetic of complex numbers in a+bi form

    Simplify arithmetic expressions involving i, including powers of i and multiplication of complex numbers in a+bi form, using i^2=-1.

  6. Complex numbers as a closure extension of the real number system

    Explain why the complex numbers were invented as a closure of the real numbers under square roots of negative numbers, comparing this invention to the earlier extension of the number system by negative numbers or irrational numbers.

  7. Quadratics disguised in non-standard form (substitution-reducible or literal-coefficient equations)

    Given an unfamiliar equation that is quadratic in form but disguised (e.g., a quartic reducible by substitution, or a quadratic with irrational or literal coefficients not resembling any worked example), determine an appropriate solution method and solve it.

  8. Reconstructing multiple equivalent forms of a quadratic from a graph, including the ambiguity of scale

    Given a graph of a parabola with no visible equation, generate all three algebraic forms (standard, factored where real roots exist, vertex) consistent with the graph, and identify which piece of information the graph does not uniquely determine (the leading coefficient's exact value versus its sign) without an additional point.

  9. The definition of the imaginary unit i

    Recall the definition of i and state that i^2 = -1.

  10. The three algebraic forms of a quadratic and their visible features

    Classify a set of given quadratic expressions by which form (standard, factored, vertex) they are already written in, and identify what information is immediately visible in each.

Polynomial Functions: Zeros, Behavior, and the Structure of Degree npeek inside ▸

Same factoring skills from Unit 1, now applied to polynomials with more than two factors, cubics, quartics, and beyond. Your child learns that a factored equation and a graph's x-intercepts are the same information in two different outfits, that a repeated factor changes the shape of the graph at that point, and that you can predict which way the far left and right ends of a graph point without plotting a single value.

  1. Multiplicity of a zero as the exponent on its linear factor

    Given a factored polynomial, identify each zero and state its multiplicity by counting repeated linear factors.

  2. Polynomial long division algorithm

    Divide a polynomial by a linear binomial using long division and state the quotient and remainder.

  3. The logical equivalence between a zero of p and (x-a) being a factor (Remainder/Factor Theorem)

    Explain why the Remainder Theorem guarantees that p(a) = 0 if and only if (x - a) is a factor, connecting the division algorithm to the factor-zero relationship.

  4. The Rational Root Theorem as a search-space-narrowing tool

    Use the Rational Root Theorem to generate a finite list of candidate zeros for a degree 3-4 polynomial with integer coefficients, and test candidates using synthetic division.

  5. Factoring by grouping for higher-degree polynomials

    Factor a degree-3 or degree-4 polynomial by grouping when four or more terms share a groupable structure.

  6. The graphical signature of even vs. odd multiplicity

    Predict whether a zero's graph crosses or touches (flattens against) the x-axis based on whether its multiplicity is odd or even.

  7. End behavior as a function of degree parity and leading coefficient sign

    Determine end behavior of a polynomial from the parity of its degree and the sign of its leading coefficient, without evaluating any points.

  8. A polynomial's graph as the joint product of zeros-with-multiplicity and end behavior

    Sketch a rough graph of a polynomial given its factored form, using zeros, multiplicities, and end behavior together, without plotting intermediate points.

  9. Reverse-construction of a polynomial equation from graphical/verbal constraints

    Construct a polynomial's equation in factored form given a verbal description of its zeros with multiplicities, its end behavior, and one additional point to fix the leading coefficient.

  10. Expansion as a check on a factored-form construction

    Verify a constructed polynomial equation by expanding it and checking that the given point satisfies the expanded form.

  11. Factored form vs. standard form as different windows onto the same polynomial

    Compare a polynomial's factored form and its expanded (standard) form and identify what each form makes visible or hides (zeros vs. sum/leading behavior).

Rational Expressions and Functions: When Division Doesn't Finishpeek inside ▸

This unit is about fractions where the top and bottom are polynomials. The core idea is that these functions behave normally almost everywhere, except at a few specific breakdown points, and whether a breakdown point is a harmless hole or an actual asymptote (a line the graph can't touch) is something you can tell from the factored equation alone, without even seeing the graph.

  1. Domain restrictions of a rational expression, found before simplifying

    Given a rational expression in factored or factorable form, state its domain by identifying every value that makes the ORIGINAL (unsimplified) denominator equal to zero.

  2. The distinction between a hole (removable discontinuity) and a vertical asymptote in a rational function

    Classify a given break in a rational function's graph as a hole or a vertical asymptote by determining whether the corresponding factor cancels between numerator and denominator, and explain why cancellation produces a removable point rather than unbounded behavior.

  3. Multiplication and division of rational expressions

    Multiply and divide two rational expressions with polynomial numerators/denominators by factoring first, then canceling common factors before multiplying out.

  4. Addition and subtraction of rational expressions with unlike denominators

    Add and subtract rational expressions with unlike polynomial denominators by constructing a correct least common denominator built from the factored form of each denominator.

  5. The relationship between algebraic equivalence of two rational expressions and their domains

    Given two rational expressions that appear different, determine whether they represent the same function everywhere or differ at specific excluded points, by comparing their domains after full factoring.

  6. Solving rational equations and identifying extraneous solutions

    Solve a rational equation by clearing denominators using the LCD, then determine which resulting solutions are valid by checking each one against the original equation's restrictions.

  7. Horizontal asymptote behavior as a ratio of leading-term end behaviors

    Predict the horizontal asymptote (or absence of one) for a rational function by comparing the degrees of its numerator and denominator, extending end-behavior reasoning about dominant terms from polynomial functions to ratios of polynomials.

  8. Structural justification of hole versus asymptote using factored form, independent of graphical appearance

    Given two visually similar graphs of rational functions, one with a hole and one with a vertical asymptote at the same apparent location, justify the structural difference using only the factored equations, without relying on visual features of the graph.

  9. Construction of a rational function from specified structural features

    Construct a rational function equation that satisfies a specified combination of features (e.g., exactly one hole, one vertical asymptote, and a given horizontal asymptote), working backward from graphical structure to symbolic form.

Radical Functions, Rational Exponents, and Inverse Functionspeek inside ▸

Two things happen here that connect at the end. First, exponent rules your child already trusts (like x^2 * x^3 = x^5) get extended to fractional exponents, so square roots and cube roots turn out to be the same thing as exponents in disguise. Second, 'inverse' gets a real definition, not every function can be undone, and the horizontal line test tells you which ones can.

  1. The definition of a rational exponent as an extension of integer exponent rules

    Given the integer exponent product rule, derive the value that a rational exponent like x^(1/2) or x^(1/3) must represent, and state the general rule x^(m/n) = (n-th root of x)^m.

  2. Simplification of radical/rational-exponent expressions and denominator rationalization

    Simplify radical and rational-exponent expressions (including products, quotients, and powers of powers) by applying integer exponent rules, and rationalize a denominator containing a single radical term.

  3. Radical equations and the extraneous-solution check

    Solve a radical equation by isolating the radical, raising both sides to the appropriate power, solving the resulting equation, and checking every candidate solution in the ORIGINAL equation to identify extraneous solutions.

  4. The non-reversibility of squaring as the mechanism producing extraneous solutions

    Explain why squaring both sides of a radical equation can introduce a solution that does not satisfy the original equation, in terms of which values of x make the squared equation true versus the original equation true.

  5. The horizontal line test and the formal definition of a one-to-one function

    Given a function's graph or equation, determine whether it is one-to-one using the horizontal line test (from a graph) or by reasoning about repeated outputs (from an equation), and state whether an inverse function exists.

  6. The structural distinction between one-to-one and many-to-one functions as it determines invertibility

    Compare a one-to-one function's graph against a many-to-one function's graph (contrasting cases) to identify what structural feature of the many-to-one graph makes the swap-coordinates procedure fail to produce a function, and generalize this into the horizontal line test rule.

  7. The algebraic procedure for finding and verifying an inverse function by composition

    Find the algebraic inverse of a one-to-one function by swapping x and y and solving for y, and verify the result is correct by showing f(g(x)) = x and g(f(x)) = x.

  8. Domain restriction as the method for creating an invertible piece of a non-one-to-one function

    Given a squaring-type function that fails the horizontal line test, restrict its domain to the smallest piece that both contains a given reference point and makes the function one-to-one, then find and verify the inverse of that restricted function.

  9. Invertibility determined from algebraic structure alone, generalized beyond graphed function families

    Determine, without graphing, whether an inverse function exists for a given algebraic rule from an unfamiliar function family, and justify the determination using only algebraic reasoning about repeated outputs.

  10. Discriminant interpretation and rational-equation extraneous solutions, as long-retention targets

    Recall the meaning of the discriminant (from Unit 1) in a new context and identify an extraneous solution in a rational equation (from Unit 3) on an un-cued delayed check.

Exponential and Logarithmic Functions: Two Kinds of Changepeek inside ▸

This unit explains why money in a savings account, a shrinking population of bacteria, and radioactive decay all follow the same kind of math, and why a logarithm isn't some separate weird topic, but just the question 'what power do I need?' asked formally. The single most important skill in this unit is telling from a table of numbers whether something is growing by the same AMOUNT each time (linear) or the same PERCENT each time (exponential), mixing these up is the most common real-world math mistake there is.

  1. The distinguishing tests for linear, quadratic, and exponential tables (constant difference, constant second difference, constant ratio)

    Given a table of values, determine whether it shows constant absolute change, accelerating change, or constant relative (percent) change, and name the family (linear, quadratic, exponential).

  2. Exponential growth/decay models built from a stated percent rate

    Write an exponential function of the form y = a(1+r)^t or y = a(1-r)^t directly from a verbal description of a percent increase or decrease situation.

  3. The logarithm as the inverse function of an exponential

    Explain why log_b(x) is defined as the inverse of b^x, using the inverse-function schema (swap x and y, undo the operation) established in Unit 4.

  4. Logarithm properties (product, quotient, power) as restatements of exponent rules

    Derive the product, quotient, and power properties of logarithms from the corresponding exponent rules rather than recalling them as separate rules.

  5. Exponential equations solved via logarithms

    Solve exponential equations of the form ab^(ct) = d by rewriting as a logarithm and evaluating with technology.

  6. Logarithmic equations and their domain restrictions

    Solve logarithmic equations, including checking for extraneous solutions created by the restricted domain of the logarithm.

  7. Model selection and construction among linear, quadratic, and exponential families for an unfamiliar context

    Given a real-world scenario (investment, population, decay, or a table framed as a mystery context) not previously seen in class, select the correct function family and construct a model that fits, defending the choice using the appropriate test.

  8. The long-run divergence of linear versus exponential processes despite short-run similarity

    Compare a constant-percent-change process to a constant-absolute-change process that produce similar values over a short early interval, and explain why they diverge over a longer time frame.

Trigonometric Functions: Modeling Periodic Behaviorpeek inside ▸

Sine and cosine get rebuilt from the ground up using the unit circle, instead of leftover right-triangle ratios from geometry. The new ideas are radians (an angle measure connected to actual arc length, not an arbitrary unit), sine and cosine as coordinates that repeat forever, and treating things like daylight hours or a Ferris wheel as transformation problems, using the same shift/stretch/reflection vocabulary from Units 1, 2, and 5.

  1. Radian measure as arc length on the unit circle

    Given an angle measured as a rotation, state the radian measure as the length of the corresponding arc on a unit circle, and convert between degree and radian measure.

  2. Unit circle definition of sine and cosine as coordinates

    Given any angle in standard position (including angles beyond 360 degrees or negative angles), identify the coordinates of the corresponding point on the unit circle as (cos theta, sin theta) and state the sign of each in each quadrant.

  3. Periodicity as a structural property, contrasted against monotonic exponential behavior

    Explain why sine and cosine are periodic functions with period 2pi by reasoning from repeated full rotations around the unit circle, and contrast this explicitly with the monotonic long-run behavior of exponential functions from Unit 5.

  4. Amplitude, midline, and period as vertical stretch, vertical shift, and horizontal stretch of sine/cosine

    Given a sine or cosine function in the form y = A sin(B(x - C)) + D, identify amplitude, midline, period, and horizontal shift, and graph the function by applying vertical stretch, vertical shift, and horizontal stretch to the parent function.

  5. Fitting a sine/cosine model to features of periodic data

    Given a real periodic data set (e.g., daylight hours by day of year) presented as a table or scatterplot, determine amplitude, midline, and period directly from the data features and write a sine or cosine equation that models it.

  6. Extrapolation from a periodic model versus a monotonic model

    Use a constructed sine/cosine model to predict a value at an input outside the range of the original data set, and justify why the periodic structure supports extrapolation differently than a polynomial or exponential model would.

  7. The Pythagorean identity derived from the unit circle

    Prove that sin^2(theta) + cos^2(theta) = 1 follows from the Pythagorean theorem applied to the unit circle, and use the identity to find one trig value given another and the quadrant.

  8. Recognizing and modeling an unfamiliar periodic context using the unit-circle-derived sine/cosine schema

    Given a novel periodic phenomenon described only in words and numbers (not sine/cosine language), such as a Ferris wheel or a pendulum, decide whether a sine/cosine model applies and construct one, generalizing the daylight-hours procedure to a structurally different but analogous situation without being told which family fits.

Sequences and Series: Discrete Growth as a Special Casepeek inside ▸

No new kind of growth here, this unit shows that arithmetic sequences are just linear functions and geometric sequences are just exponential functions, both restricted to whole-number inputs (1st term, 2nd term, 3rd term...), wearing new vocabulary. The unit closes with adding up a finite list of geometric terms (genuinely new), and a first honest look at adding infinitely many numbers and getting a finite answer.

  1. The structural distinction between arithmetic (constant additive difference) and geometric (constant multiplicative ratio) sequences

    Given a sequence presented as a list of terms, a table, or a context, identify whether it is generated by repeated addition or repeated multiplication and state which.

  2. The explicit formula for arithmetic and geometric sequences

    Given the first term and common difference (or ratio) of a sequence, generate the explicit formula a(n) = a1 + (n-1)d [or a(n) = a1 * r^(n-1)] and use it to compute a specified term.

  3. The correspondence between sequence formulas and their parent continuous functions (linear and exponential)

    Explain why the explicit formula for an arithmetic sequence has the same algebraic structure as a linear function's slope-intercept form, and why the geometric explicit formula mirrors exponential y = a*b^x, by identifying which part of each formula plays the role of rate/ratio and which plays the role of starting value.

  4. The conversion between recursive and explicit representations of arithmetic and geometric sequences

    Given a recursive formula for a sequence, produce the equivalent explicit formula, and given an explicit formula, produce the equivalent recursive formula.

  5. The finite geometric series sum formula and the multiply-and-subtract structure that produces it

    Derive the formula for the sum of a finite geometric series by examining the structure of S - rS for a specific numeric series, then generalize the pattern to symbolic a, r, n.

  6. Arithmetic vs. geometric sequence models applied to unfamiliar real-world contexts

    Given a real-world context (loan payments, medication decay, bouncing ball height, population with constant migration), determine whether an arithmetic model, a geometric model, or neither fits, and justify the choice using the pattern of successive differences or ratios in the data.

  7. Convergence of an infinite geometric series when |r| < 1 and the sum formula S = a/(1-r)

    Given an infinite geometric series with |r| < 1 presented visually (e.g., a square repeatedly divided in half) and numerically, explain informally why the partial sums approach a finite limit and compute that limit using S = a/(1-r).

  8. Discrimination between arithmetic and geometric sequence structure under confusable surface conditions

    Given two unfamiliar sequences side by side, one arithmetic and one geometric, with surface features deliberately similar (same first term, similarly sized second term), select the correct classification and formula type for each and explain what distinguishes them, without being told in advance which is which.

Statistics: Modeling and Trusting Datapeek inside ▸

This is the last unit, and it's where all seven prior function families get put to work on real, messy data. The first half is about picking the right kind of curve to fit data and checking how well it actually fits (using leftover errors called residuals). The second half switches gears entirely, from fitting models to trusting them, sampling bias, correlation versus causation, and reading conditional probability from a table, so your child can push back on a sloppy headline instead of just believing it.

  1. The empirical (68-95-99.7) rule for normal distributions

    Given a data set's mean and standard deviation, estimate the percentage of values within 1, 2, or 3 standard deviations using the empirical rule.

  2. Appropriateness conditions for the normal-distribution model

    Judge, from a histogram or dot plot, whether a normal-distribution model is an appropriate fit for a given data set, citing skew, bimodality, or outliers as disqualifying features.

  3. The constant-difference/constant-ratio diagnostic for choosing a regression family

    Classify a scatter plot's pattern of first differences, ratios, or curvature to select linear, quadratic, or exponential as the candidate regression family, applying Unit 5's constant-difference/constant-ratio test.

  4. Residuals and residual plots as evidence of model fit

    Compute residuals for a fitted regression model and interpret a residual plot's pattern as evidence for or against the chosen function family.

  5. Function-family selection and extrapolation risk for a novel data set

    Given an unfamiliar real data set with no family cue in the prompt, select, fit, and justify a function family using residual evidence, then state an explicit limitation on extrapolation.

  6. Sampling method and its relationship to bias

    Distinguish a random sample from a convenience or self-selected sample in a described study, and identify how that sampling method could bias reported results.

  7. The distinction between correlation and causation

    Explain why a strong correlation between two variables in a study does not by itself establish that one causes the other, using a specific plausible confound.

  8. Conditional probability from two-way tables

    Calculate a conditional probability from a two-way frequency table and use it to evaluate whether a reported study result depends on an unstated condition.

  9. Evaluation criteria for reports based on data

    Critique a real published or simulated news report of a study by identifying at least two of: sampling flaw, correlation/causation overreach, margin-of-error omission, or extrapolation beyond the data range.

  10. Structural discrimination between quadratic and exponential fit given similar-looking scatter data

    Compare two data sets with visually similar scatter plots but different residual patterns to determine which one exponential and which one is quadratic, using structural features rather than surface curve shape alone.

From the parent guide

This is the algebra course that takes "graphing parabolas" from Algebra I and blows it out into six more families of functions, polynomials, rational expressions, radicals, exponentials/logs, trig, and finally sequences and statistics. The thread running through all eight units is one question asked over and over in new clothes: given an equation, what does the graph look like, and given a graph or a real situation, what's the equation? Your child will get a lot of practice moving between an equation, a graph, a table, and a word problem, for each of these families, and by the end they should be able to look at data or a situation and say "that's exponential, not linear" or "that needs a hole, not an asymptote" and explain why. It's a full year of building one increasingly large toolbox rather than eight unrelated topics.

Unit 1 · what to expect

This unit takes quadratics, which your child can already factor and graph from Algebra I, and gives them three ways to write the same equation (standard, factored, vertex), a way to predict how many solutions an equation has before solving it (the discriminant), and a brand-new kind of number for when the answer to a square root is negative. The big idea is that completing the square isn't a random trick, it's the one procedure that generates vertex form AND the quadratic formula, so understanding it once explains both.

The full guide covers all 8 units: where kids get stuck, what to say, and how to tell it's working. Included with the course.

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Algebra II: Functions, Structure, and Modeling, Grade 11 Homeschool Curriculum