Stuff You Must Know Cold: Algebra 1 – Study Notes

Source: SYMKC Series, Calculus Prep (Texas A&M University)

Tags: algebra 1, powers, perfect squares, cubes, factorials, linear equations, quadratic equations, slope, inequalities, systems of equations, order of operations, properties, absolute value, functions, distance formula, midpoint, pythagorean theorem, central tendency


TL;DR

This covers the foundational algebra you need automatic recall of before moving into Algebra 2 and beyond. Perfect squares, cubes, powers of 2, linear and quadratic equation forms, slope, function definitions, and the core number properties. If you have to stop and think about any of these during a test, you are already behind.


Key Terms

Perfect square

The result of squaring an integer. You need instant recall of 13² through 25².

Factorial (n!)

The product of all positive integers from 1 to n. By convention, 0! = 1.

Slope

The rate of change between two points: rise over run. Calculated as (y₂ – y₁) / (x₂ – x₁).

Quadratic formula

The formula x = (–b ± √(b² – 4ac)) / 2a, used to find the roots of any quadratic equation ax² + bx + c = 0.

Discriminant

The expression b² – 4ac inside the quadratic formula. Determines the nature of the roots.

Domain

The set of all possible input values (x-values) for a function.

Range

The set of all possible output values (y-values) for a function.

Direct variation

A relationship of the form y = kx, where k is a constant. As x increases, y increases proportionally.

Indirect variation

A relationship of the form y = k/x. As x increases, y decreases.


Core Content

Powers – Perfect Squares

You should be able to rattle these off without calculation:

  • 13² = 169

  • 14² = 196

  • 15² = 225

  • 16² = 256

  • 17² = 289

  • 18² = 324

  • 19² = 361

  • 20² = 400

  • 21² = 441

  • 22² = 484

  • 23² = 529

  • 24² = 576

  • 25² = 625

Powers – Perfect Cubes

  • 2³ = 8

  • 3³ = 27

  • 4³ = 64

  • 5³ = 125

  • 6³ = 216

  • 7³ = 343

  • 8³ = 512

  • 9³ = 729

  • 10³ = 1,000

  • 11³ = 1,331

  • 12³ = 1,728

Powers – Fourth Powers

  • 2⁴ = 16

  • 3⁴ = 81

  • 4⁴ = 256

  • 5⁴ = 625

Powers of 2

  • 2⁵ = 32

  • 3⁵ = 243

  • 4⁵ = 1,024

  • 5⁵ = 3,125

  • 2⁶ = 64

  • 2⁷ = 128

  • 2⁸ = 256

  • 2⁹ = 512

  • 2¹⁰ = 1,024

  • 2¹¹ = 2,048

  • 2¹² = 4,096

Factorials

  • 0! = 1

  • 1! = 1

  • 2! = 2

  • 3! = 6

  • 4! = 24

  • 5! = 120

  • 6! = 720

  • 7! = 5,040

Linear Equations

  • Parent function: y = x

  • Standard form: Ax + By = C

  • Slope-intercept form: y = mx + b

  • Point-slope form: y – y₁ = m(x – x₁)

  • Slope: m = (y₂ – y₁) / (x₂ – x₁)

  • Graph: a straight line; the parent function y = x passes through the origin at 45°

Quadratic Equations

  • Parent function: y = x²

  • General form: y = ax² + bx + c

  • Standard form (vertex form): y = a(x – h)² + k

  • Intercept form (factored form): y = a(x – p)(x – q)

  • Vertex: (h, k) in vertex form; or (–b/2a, f(–b/2a)) from general form

  • Axis of symmetry: x = –b/2a

  • Quadratic formula: x = (–b ± √(b² – 4ac)) / 2a

  • Graph: a parabola opening upward if a > 0, downward if a < 0

Inequality Meanings

  • < means "less than" (open circle on a number line)

  • ≤ means "less than or equal to" (closed circle)

  • > means "greater than" (open circle)

  • ≥ means "greater than or equal to" (closed circle)

Three Ways to Solve a System of Equations

  1. Graphing – plot both equations and find the intersection point

  1. Substitution – solve one equation for a variable, substitute into the other

  1. Elimination – add or subtract equations to cancel out one variable

Order of Operations (PEMDAS)

  1. Parentheses (and other grouping symbols)

  1. Exponents (and roots)

  1. Multiplication and Division (left to right)

  1. Addition and Subtraction (left to right)

Properties of Real Numbers (using a, b, c)

Commutative property

  • Addition: a + b = b + a

  • Multiplication: ab = ba

Associative property

  • Addition: (a + b) + c = a + (b + c)

  • Multiplication: (ab)c = a(bc)

Distributive property

a(b + c) = ab + ac

Absolute Value

  • For any real number a, the absolute value is always ≥ 0

  • |a| = a if a ≥ 0; |a| = –a if a < 0

  • |–a| = |a| = a (when a ≥ 0)

Function Definitions

  • Domain: the set of all input values (x) for which the function is defined

  • Range: the set of all output values (y) the function produces

  • Function: a relation where every input has exactly one output (passes the vertical line test)

  • Direct variation: y = kx

  • Indirect variation: y = k/x

  • Roots (zeros): the x-values where f(x) = 0

Measures of Central Tendency

  • Mean: the sum of all values divided by the number of values

  • Median: the middle value when data is arranged in order

  • Mode: the value that appears most frequently

  • Range: the difference between the greatest and least values (note: this is a different use of "range" from the function definition)

Distance Formula (between two points)

d = √((x₂ – x₁)² + (y₂ – y₁)²)

Midpoint Formula

(m₁, m₂) = ((x₁ + x₂)/2, (y₁ + y₂)/2)

Distance Formula (physics)

d = rt, where r = rate and t = time

Pythagorean Theorem

a² + b² = c², where c is the hypotenuse

Parallel and Perpendicular Lines

Given y = mx + b:

  • A parallel line has the same slope: m

  • A perpendicular line has slope: –1/m (the negative reciprocal)

Dimensional Analysis

To convert between units, multiply by conversion factors so that unwanted units cancel. For example, to convert °C to °F: F = (9/5)C + 32.

Discriminant and Nature of Roots

The discriminant is b² – 4ac.

  • If b² – 4ac > 0: two distinct real roots

  • If b² – 4ac < 0: no real roots (two complex conjugate roots)

  • If b² – 4ac = 0: exactly one real root (a repeated root)

Piecewise Functions

A piecewise function uses different rules for different intervals of x. Written with a brace grouping the pieces, e.g.:

f(x) = { expression₁ if condition₁; expression₂ if condition₂ }

When graphing, pay attention to open vs closed circles at boundary points.


Why It Matters / Exam Flags

⚠️ Perfect squares 13² through 25² appear constantly in factoring, simplifying radicals, and the Pythagorean theorem. Memorise them.

⚠️ The quadratic formula is the universal fallback for any quadratic. Do not confuse the sign: it is –b, not +b.

⚠️ Discriminant = 0 means one repeated root, not "no solution." Common mix-up.

⚠️ Parallel lines share the same slope. Perpendicular slopes are negative reciprocals. Students frequently forget the negative.

⚠️ In PEMDAS, multiplication and division have equal precedence (left to right), and so do addition and subtraction. They are not strictly sequential.


Practice Q&A

Q: What is the slope of a line perpendicular to y = 3x + 7?

A: –1/3 (the negative reciprocal of 3).

Q: What does a discriminant of –4 tell you about the roots of a quadratic?

A: There are no real roots; the equation has two complex conjugate roots.

Q: State the vertex of y = 2(x – 3)² + 5.

A: The vertex is (3, 5).

Q: Evaluate 6! without a calculator.

A: 720.

Q: What is 17²?

A: 289.

Q: Name the three methods for solving a system of equations.

A: Graphing, substitution, and elimination.


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