Objective:

To use two points to write the equation of a line.

Notes:

Slope Formula:

n 1

Steps to finding the equation:

  1. Write "y = mx + b".
  2. Find the slope. (For help see section 4.4).
  3. Replace the variable m with the slope you found in step 2.
  4. Choose one of your points. Make note of its coordinates.
  5. Replace the variable x with the x-coordinate of the point from step 4 and y with the y-coordinate of the point.
  6. Solve for the only variable you have left, b.
  7. Write "y = mx + b" again.
  8. Replace m with the slope and b with the value you found in step 6.

Examples:

Solve:

  1. Write the equation of the line containing the points (−1, 1) and (0, 3).

    Ex 1


  2. Write the equation of the line containing the points (4, 4) and (−2, −1).

    Ex 2


  3. Write the equation of the line containing the points (3, −4) and (3, 8).

    Ex 3

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This page was last updated on 08/09/13.