Mrs. Agriesti's Algebra I Notes
5.1 & 5.2 Write Equations of Lines Given the Slope and a Point
Objective:
To use the slope and any point on the line to find the equation of the line.
Notes:
Steps to finding the equation:
- Write "y = mx + b".
- Find the slope by looking at the graphed line and counting the rise and run. (For help see section 4.4).
- Replace the variable m with the slope you found in step 2.
- Locate a point on the graphed line. Make note of its coordinates.
- Replace the variable x with the x-coordinate of the point from step 4 and y with the y-coordinate of the point.
- Solve for the only variable you have left, b.
- Write "y = mx + b" again.
- Replace m with the slope and b with the value you found in step 6.
Examples:
Solve:
- Write the equation of the line that passes through (8,3) with slope 4.
- Write the equation of the line that passes through (6,7) with slope 2/3.
