1. Writing Linear Equations

2. Slope and Y-Intercept
5/2/13
• To write the equation of a line:
▫ Use y = mx + b
▫ Put the given slope and y-intercept in the
equation
▫ Remember: m is slope
b is y-intercept
Answer needs both x and y in it!!

3. Examples:
• Write an equation of the line with:
• slope = -2
y-intercept = 4
• slope =
y-intercept = -1

4. • Slope = 1
y-intercept =
• Slope = -3
• y-intercept = 0

5. You Try!
• Write an equation of the line with:
• slope = 4
y-intercept = -5

6. Point-Slope Form
5/3/13
• Another form of a linear equation is
point-slope form.
• It is:
• m is still slope!
• (x1, y1) is a point on the line
• Answer still needs x and y in it!

7. Examples:
• Write an equation in point-slope form
of the line:
• Slope = 2
• Through (1, 3)
• Slope = -4
• Through (-2, -6)

8. • Slope = 1
• Through (0, 5)
• Slope = 1/3
• Through (-4, 0)

9. You Try!
• Slope = -2
• Through (3, -1)

10. Point-Slope to
Slope-Intercept Form 5/6/13
• Given a point and the slope, we can
use point-slope form.
• Remember: y – y1 = m(x – x1)
• Then, to get in slope-intercept form:
▫ Solve for y
▫ Distribute first!
▫ Add/subtract to get y alone.

11. Examples:
• Write an equation of the line with the
given slope that passes through the
given point.
• Slope = -2
• Through (1, 4)

12. • Slope = 1/3
• Through (-2, 5)
• Slope = 1
• Through (0, 8)

13. You Try!
• Write an equation of the line with
slope = -1, and through the point (4, -2).