Slope & Graphs of Lines
Slope is rise over run. Use y = mx + b to read a line.
The rules
- Slope = (y₂ − y₁) / (x₂ − x₁).
- In y = mx + b, m is the slope and b is the y-intercept.
- Parallel lines have equal slopes. Perpendicular lines have slopes that are negative reciprocals.
- To write an equation, use the slope and one point.
Watch out: Subtracting the coordinates in different orders on top and bottom.
Worked example
What is the slope of the line through (1, 2) and (5, 10)?
- Rise = 10 − 2 = 8.
- Run = 5 − 1 = 4.
- 8/4 = 2.
Answer: 2
Try it yourself
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