1. Remember that a line can be expressed as y = mx+b, where m is the slope and b is the y intercept (where the line hits the y axis).

2. Remember that slope can be described as rise over run – the difference in the y values divided by the difference in the x values.

3. In this instance -- R(-5,4) and S(7,2) – the rise is 2-4, or -….and the run is 27- (-5), or 12.

4. The slope, therefore is

5. The equation is therefore y= -x+b.

6. We can figure out b by plugging in any coordinate on the line, such as 7,2.

a. So, 2= -*7+b.

b. b=.

7. Therefore, y=--x +