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Writing the equation of a line from two points worksheets Grade 8

Find the slope from two points, then the y-intercept, and write the equation.

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Free · Worked example · 9 problems · Answer key · US Letter

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How to do it

Find the slope first. Then use one point to find b.

Through (4,−24) and (5,−29):y=−5x−4\text{Through }(4, -24)\ \text{and }(5, -29):\quad y = -5x - 4
−29−(−24)5−4=−51=−5\dfrac{-29 - (-24)}{5 - 4} = \dfrac{-5}{1} = -5change in y over change in x
−24=(−5)(4)+b-24 = (-5)(4) + bput m = −5 and the point (4, −24) into y = mx + b
−24=−20+b-24 = -20 + b
b=−4b = -4add 20 on both sides
y=−5x−4y = -5x - 4

Example problems

  1. Through (−4,14) and (−6,24):\text{Through }(-4, 14)\ \text{and }(-6, 24):\quad
  2. Through (−6,2) and (−4,4):\text{Through }(-6, 2)\ \text{and }(-4, 4):\quad
  3. Through (−5,−10) and (6,1):\text{Through }(-5, -10)\ \text{and }(6, 1):\quad
  4. Through (−5,11) and (−4,10):\text{Through }(-5, 11)\ \text{and }(-4, 10):\quad

Linear equations and systems

  1. Finding slope from two points
  2. Slope and y-intercept
  3. Slope and intercept from a graph
  4. Writing the equation of a line from a slope and a point
  5. Writing the equation of a line from two points
  6. Standard form to slope-intercept form
  7. Solving systems of equations by substitution
  8. Solving systems of equations by elimination