The document provides examples of determining the equation of a line given information about its slope and a point it passes through. It works through four examples, finding the equation of a line with slope 7 and y-intercept -4, slope -4/5 passing through (1,3), slope 2/3 passing through (8,1), and slope 1/9 passing through (-2,5). The examples demonstrate how to set up and solve systems of equations to determine the y-intercept and write the equation in y=mx+b form.

1. So far we have looked at equations of
lines and determined information
about the line in order to graph it.
Today we are going to do the reverse.

2. A line has slope 7 and a y-intercept of
-4, what is the equation of the line?

3. A line has slope -4/5 and goes through point
(1,3) what is the equation of the line?

4. A line has slope 2/3 and goes through point
(8,1) what is the equation of the line?
y = 2/3x + b
1 = 2/3(8) + b
1 - 16/3 = b
3/3 - 16/3 = b
-13/3 = b

5. A line has slope 1/9 and goes through point
(-2,5) what is the equation of the line?
y = 1/9x + b
5 = 1/9(-2) + b
5 = -2/9 + b
5 + 2/9 = b
47/9 = b

6. A line has slope 4 and goes through point
(2,1) what is the equation of the line?

8. What is the equation of this line?
b=2
m = -1
y = -1x + 2