Algebra 2 Cheat Sheet

1. Basic Concepts

1.1 Complex Numbers

Complex numbers are numbers that have a real part and an imaginary part. The standard form is \(a + bi\), where \(a\) is the real part and \(bi\) is the imaginary part.

Operations:

Example 1:

Add the complex numbers \( (3 + 2i) \) and \( (1 - 4i) \).

Example 2:

Multiply the complex numbers \( (2 + 3i)(1 - 2i) \).

1.2 Polynomials

A polynomial is an expression consisting of variables (also called indeterminates) and coefficients, involving operations of addition, subtraction, multiplication, and non-negative integer exponents of variables.

Key Concepts:

Example 1: Factoring

Factor the polynomial \(4x^3 - 8x^2 + 16x\).

Example 2: Polynomial Division

Divide \(x^3 + 2x^2 - 5x - 6\) by \(x - 2\) using synthetic division.

1.3 Functions and Their Properties

A function is a relation between a set of inputs (domain) and a set of possible outputs (range) where each input is related to exactly one output.

Key Concepts:

Example:

Find the domain and range of the function \(f(x) = \frac{1}{x-2}\).

2. Equations and Inequalities

2.1 Quadratic Equations

A quadratic equation is a second-degree polynomial equation of the form \(ax^2 + bx + c = 0\).

Solving Methods:

Discriminant: The expression \(b^2 - 4ac\) indicates the nature of the roots:

Example:

Solve the quadratic equation \(x^2 + 4x + 3 = 0\) by factoring.

2.2 Rational Equations

Rational equations involve fractions with polynomials in the numerator and denominator.

Steps to Solve:

Asymptotes: Identify vertical, horizontal, and slant asymptotes based on the degree of the numerator and denominator.

Example:

Solve the rational equation \( \frac{2x}{x - 3} = \frac{4}{x + 2} \).

2.3 Exponential and Logarithmic Equations

Exponential equations have the form \(a^x = b\), and logarithmic equations have the form \(\log_b(x) = y\).

Key Properties:

Solving Steps:

Example 1: Exponential Equation

Solve \(3^{2x + 1} = 81\).

Example 2: Logarithmic Equation

Solve \(\log_2(x + 3) = 4\).

3. Functions

3.1 Linear Functions

A linear function is a function of the form \(y = mx + b\), where \(m\) is the slope and \(b\) is the y-intercept.

Key Forms:

Example:

Find the equation of a line with slope 3 passing through the point (2, -1).

3.2 Quadratic Functions

A quadratic function is a function of the form \(y = ax^2 + bx + c\). It graphs as a parabola.

Key Forms:

Example:

Convert the quadratic function \(y = 2x^2 + 8x + 5\) to vertex form.

3.3 Polynomial Functions

Polynomial functions are functions that are represented by polynomials. The degree of the polynomial determines the behavior of the graph at the ends (end behavior).

Key Concepts:

Example:

Determine the end behavior of the polynomial function \(f(x) = -2x^3 + 3x^2 - x + 1\).

3.4 Rational Functions

Rational functions are functions of the form \(f(x) = \frac{p(x)}{q(x)}\), where \(p(x)\) and \(q(x)\) are polynomials and \(q(x) \neq 0\).

Asymptotes:

Example:

Identify the vertical and horizontal asymptotes of the function \(f(x) = \frac{x^2 - 1}{x - 2}\).

3.5 Exponential and Logarithmic Functions

Exponential functions have the form \(f(x) = a \cdot b^x\), where \(a\) and \(b\) are constants, and \(b > 0\). Logarithmic functions are the inverse of exponential functions and have the form \(f(x) = \log_b(x)\).

Graphing:

Example 1: Exponential Function

Graph \(f(x) = 2^x\).

Example 2: Logarithmic Function

Graph \(f(x) = \log_2(x)\).

4. Sequences and Series

4.1 Arithmetic Sequences

An arithmetic sequence is a sequence of numbers in which the difference between consecutive terms is constant. The general term of an arithmetic sequence is given by \(a_n = a_1 + (n - 1)d\), where \(a_1\) is the first term and \(d\) is the common difference.

Sum of n Terms:

Example:

Find the sum of the first 20 terms of the arithmetic sequence 2, 5, 8, ...

4.2 Geometric Sequences

A geometric sequence is a sequence of numbers where each term after the first is found by multiplying the previous term by a fixed, non-zero number called the common ratio. The general term of a geometric sequence is given by \(a_n = a_1 \cdot r^{(n-1)}\), where \(a_1\) is the first term and \(r\) is the common ratio.

Sum of n Terms:

Example:

Find the sum of the first 5 terms of the geometric sequence 3, 6, 12, ...

4.3 Series

A series is the sum of the terms of a sequence. For arithmetic and geometric series, there are specific formulas to calculate the sum of the first \(n\) terms.

Infinite Geometric Series:

Example:

Find the sum of the infinite geometric series \( \frac{1}{3} + \frac{1}{9} + \frac{1}{27} + \dots \)

5. Conic Sections

5.1 Parabolas

A parabola is the graph of a quadratic function. The standard form of a parabola is \(y = ax^2 + bx + c\) or \(x = ay^2 + by + c\).

Vertex Form:

Example:

Find the vertex of the parabola \(y = 2x^2 - 8x + 6\).

5.2 Circles

A circle is a set of all points in a plane that are equidistant from a fixed point called the center. The standard form of the equation of a circle is \((x - h)^2 + (y - k)^2 = r^2\), where (h, k) is the center and \(r\) is the radius.

Example:

Write the equation of a circle with center at (3, -2) and radius 5.

5.3 Ellipses

An ellipse is a set of all points in a plane where the sum of the distances from two fixed points (the foci) is constant. The standard form of an ellipse is \(\frac{(x - h)^2}{a^2} + \frac{(y - k)^2}{b^2} = 1\), where (h, k) is the center, \(a\) is the distance from the center to a vertex along the major axis, and \(b\) is the distance from the center to a vertex along the minor axis.

Example:

Write the equation of an ellipse with center at (0, 0), a major axis of length 10 along the x-axis, and a minor axis of length 6 along the y-axis.

5.4 Hyperbolas

A hyperbola is a set of all points in a plane where the difference of the distances from two fixed points (the foci) is constant. The standard form of a hyperbola is \(\frac{(x - h)^2}{a^2} - \frac{(y - k)^2}{b^2} = 1\) (horizontal hyperbola) or \(\frac{(y - k)^2}{a^2} - \frac{(x - h)^2}{b^2} = 1\) (vertical hyperbola).

Asymptotes: The asymptotes of a hyperbola are the lines that the hyperbola approaches but never touches. For a hyperbola centered at (h, k), the asymptotes are given by the equations \(y - k = \pm \frac{b}{a}(x - h)\) (horizontal hyperbola) or \(y - k = \pm \frac{a}{b}(x - h)\) (vertical hyperbola).

Example:

Write the equation of a hyperbola with center at (1, -2), a horizontal transverse axis, \(a = 4\), and \(b = 3\).