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  • Grade 8
  • Two points, whole answers

Line equation from two points worksheets

Two points fix a line, and turning them into y = mx + b is a real two-step: the slope has to be found before the intercept can be. These free printable worksheets give two points and ask for the whole equation.

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Ready to printLine equation from two points
Line equation from two points worksheet — Two points, whole answers, free printable with answer key

The answer key prints on a separate page.

What's on this sheet

The slope comes first, as (y₂ − y₁) ÷ (x₂ − x₁): for (1, 3) and (3, 7) that is (7 − 3) ÷ (3 − 1) = 2. Then one of the points goes back in to back out the intercept — 3 = 2 · 1 + b gives b = 1 — so the line is y = 2x + 1. Where the combined writing-linear-equations sheet also offers the easier slope-and-a-point questions, this page uses two points every time, so the slope step is never skipped.

Why this sheet works

The order is the whole discipline: a child who reaches for the intercept before the slope has nothing to substitute, because b depends on m. Every step-by-step walk here finds the slope, then substitutes a point, then reports both — and a child who stops at the slope has only half an answer.

How this one works

One question from this sheet, worked through a step at a time.

Write the equation of the line through (2, 3) and (4, 5)

slope = 2 ÷ 2=1
b = 3 − (1)(2)=1
y = x + 1
  1. Find the slope first: rise over run, (5 − 3) ÷ (4 − 2) = 1.
  2. Put a point back in to find b: b = y − mx = 3 − (1)(2) = 1.
  3. Write it as y = mx + b: y = x + 1.