1. Writing Equations of Lines
CG-L6 Objectives: To determine the slope y-intercept form of a line given various inputs.
Learning Outcome B-4

2. Plot the following equations in Winplot, on the same screen.
These equations are all in the form y = mx. What is m?
Theory – Deriving the Equation of a Line

3. Plot the following equations in Winplot, on the same screen.
These equations are all in the form y = mx + b (where m is 1). What is b?
Theory – Deriving the Equation of a Line

4. Predict the line for each equation shown
Predict the line for each equation shown. State slope & y-intercept for each case.
Example 1 – Two Points

5. A Line is just a collection of points.
The Slope, Y-Intercept Form of the Line describes a straight line with slope of m and y-intercept b.
A Line is just a collection of points.
The coordinates (x,y) of each point on the line will work in the equation (make the equation true).
Find three points on each line shown:
Example 1 – Two Points

6. (-1,1) (0,-2) (50,-49) Determine if the point is on the line.
Example 1 – Two Points

7. The equations of horizontal and vertical lines look a little different
The equations of horizontal and vertical lines look a little different. We can understand their equations by considering each to be collections of points, at a common distance from an axis.
Horizontal Lines
Vertical Lines
Example 2 – Two Points (Special Case)

8. Write the equation for each line.
Example 3 – Two Points (Special Case)

9. Write the equation for each line.
Example 3 – Two Points (Special Case)

10. passes through slope y-intercept equation 4 1 -1/6 -3 (1,3) 2
Write equations in the form y = mx + b for the following straight lines.
passes through slope y-intercept equation
4 1
-1/6 -3
(1,3) 2
(0,3) -1/2
(-3,-2) (0,1)
(4,3) -1
(-1,0) 0
(5,6) undefined
Example 4 – Given Slope, One Point

11. Write equations in the form y = mx + b for the following straight lines. (Hint: use the slope formula to find m, then substitute either point to find b)
passes through and
(-1,-2) (1,2)
(-4,-4) (2,-1)
Example 4 – Given Slope, One Point