What is the golden rule of solving equations?
Whatever you do to one side, do to the other.
If ax = 0, what must be true?
Either a = 0 or x = 0.
Distributive property formula?
a(b + c) = ab + ac
How do you solve a proportion a/b = c/d?
Cross-multiply: ad = bc.
If x² = 16, what are possible values of x?
4 and −4.
Difference of squares formula?
a² − b² = (a − b)(a + b)
Take the same numbers, one minus and one plus.
Multiply them.
The middle disappears.
Only the squares remain.
Perfect square trinomial formula?
a² + 2ab + b² = (a + b)²
If (x + a)(x + b) expands, what is the middle term?
(a + b)x
What is slope formula?
(y₂ − y₁)/(x₂ − x₁)
Slope-intercept form?
y = mx + b
What does slope represent?
Rate of change.
Parallel lines have what in common?
Same slope.
Perpendicular slopes relationship?
Negative reciprocals.
If multiplying or dividing an inequality by a negative, what happens?
Flip the inequality sign.
Exponent rule: xᵃ · xᵇ = ?
xᵃ⁺ᵇ
Exponent rule: (xᵃ)ᵇ = ?
xᵃᵇ
Exponent rule: x⁻ᵃ = ?
1 / xᵃ
What is the quadratic formula?
x = (-b ± √(b² − 4ac)) / 2a
What does discriminant (b² − 4ac) tell you?
Number and type of solutions.
If discriminant > 0?
Two real solutions.
If discriminant = 0?
One real solution.
If discriminant < 0?
No real solutions.
How do you solve systems quickly when equations are aligned?
Use elimination.
When is substitution better?
When one variable is already isolated.