Find the slope of the line going through the points (-9, -6) and (-18, -6).
+ The equation is y = ax+b
+ we have -6= -9a+b or b= 9a- 6
and the second: -6= -18a+b or -6= -18a+ 9a-6 or -9a=0 and a=0, b= 9*0-6= -6
The equation is: y= -6
and the slope is a=0