Activity (Process)

Finding an Equation of a Line Given Two Points

When two points on a line are known but the slope is not given directly, the equation of the line can be found using this four-step procedure:

  1. Find the slope using the two given points.
  2. Choose one of the two points to use as (x1,y1)(x_1, y_1).
  3. Substitute the slope and the chosen point's coordinates into the point-slope form: yy1=m(xx1)y - y_1 = m(x - x_1).
  4. Simplify and rewrite the equation in slope-intercept form y=mx+by = mx + b.

Either point may be used in Step 2 — both will yield the same final equation. The extra initial step of computing the slope from the two points is the only difference from the slope-and-a-point method.

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Updated 2026-04-23

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