Illustrative Mathematics / Open Up Resources HS Algebra 1 (2021) by the Illustrative Mathematics team (William McCallum, lead). HS Algebra 1 textbook in the IM/OUR HS Math curriculum, openly licensed (CC BY 4.0) and free to use; problem-based, IM-aligned (this IS the canonical IM-aligned course).
One-variable linear equations: simple equations, multi-step, equations with variables on both sides, absolute value equations, and rewriting equations and formulas (literal equations).
Linear inequalities in one variable: writing and graphing inequalities; addition, subtraction, multiplication, and division properties; multi-step, compound, and absolute value inequalities.
Functions and function notation; linear functions; graphing in standard and slope-intercept form; transformations of graphs of linear functions; absolute value functions.
Writing equations of lines in slope-intercept form, point-slope form, and forms for parallel/perpendicular lines; scatter plots and lines of fit; arithmetic sequences as linear functions.
Systems of two linear equations in two variables: graphing, substitution, elimination; special systems (no solution / infinite solutions); equations by graphing; linear inequalities and systems of linear inequalities in two variables.
Properties of exponents; radicals and rational exponents; exponential functions, growth and decay; solving exponential equations; geometric sequences and recursively defined sequences.
Polynomials: addition, subtraction, multiplication, special products; solving polynomial equations in factored form; factoring trinomials with leading coefficient 1 and != 1; factoring special products; complete factoring.
Graphing quadratic functions in various forms: f(x) = ax^2, ax^2 + c, ax^2 + bx + c, vertex form a(x-h)^2 + k, and intercept form; comparing linear, exponential, and quadratic functions.
Properties of radicals; solving quadratic equations by graphing, square roots, completing the square, and the quadratic formula; solving nonlinear systems of equations.
Graphing square root and cube root functions; solving radical equations; inverse of a function.