Formula
\( m = \dfrac{y_2 - y_1}{x_2 - x_1} \)
RISE over RUN = up ÷ across
Slope-Intercept
\( y = mx + b \)
m = slope · b = y-intercept
Positive / Negative
↗ positive · ↘ negative
→ zero · ↕ undefined
PNZU — Plus, Negative, Zero, Undefined
Parallel & Perpendicular
∥ same slope: \(m_1 = m_2\)
⊥ neg. reciprocal: \(m_1 \cdot m_2 = -1\)
FLIP + SIGN CHANGE for ⊥
Standard Form → Slope
\(Ax + By = C\)
slope \( = -\dfrac{A}{B} \) · negative A over B
Steepness Trick
|m| bigger → steeper
|m| = 1 → 45°
BIGGER absolute value = STEEPER line