Okay so a perpendicular line has a slope of the opposite reciprocal so for example in this equation the slope is 2 so the slope of a perpendicular equation would be -1/2 now since you know that you can put that in the slope intercept equation Now you have y=-1/2x+b and since you have a point (point A) you can plug it in and solve for b -8=-1/2(4)+b -8=-2+b b=-6 Now you have both parts simply put it in and you have the equation y=-1/2x-6 I also attached the image with both to prove they are perpendicular