Because the standard slope equation is y=mx+b and in perpendicular lines the slope is opposite of the slope on a parallel line. 0.25 is equal to 1/4 and the opposite of 1/4 is 4/1 but you also make it negative so it’s -4. So we have y=-4x+b and you plug in the coordinates and solve [8=-4(-6)+b and -4*-6=24 so you rewrite it as 8=24+b and 8-24=-16 and -16=b] so you plug in b and the equation is y=-4x-16
