Strategy #7: Understand Slope and Linear Graphs

Category: Algebra

Slope = rise/run = (y₂ − y₁)/(x₂ − x₁). The y-intercept is where the line crosses the y-axis (set x = 0).

Why it matters: Linear equations appear constantly on the SAT in the form y = mx + b (slope-intercept) and Ax + By = C (standard form). You need to move fluidly between these forms.

Key facts:

• Parallel lines have equal slopes

• Perpendicular lines have slopes that are negative reciprocals (m₁ × m₂ = −1)

• A horizontal line has slope 0; a vertical line has undefined slope

Practice tip: Given any two points, always compute slope first, then use one point to find the y-intercept.