A better way is to use the formula for the distance from a point to a line. Here's that way: The distance from the point (x1,y1) to the line Ax+By+C=0 is given by the formula:The line y= -4x-30 is the line 4x+y+30 = 0 So the radius r = And the radius squared is r2 = 17 , and the center is (h,k) = (-4,3), so the equation of that circle is (x-h)2+(y-k)2 = r2 or (x+4)2+(y-3)2 = 17 Edwin