slope of P : using 2 points and slope formula : (y2 - y1) / (x2 - x1)
(0,-4),(2,2)
slope = (2 - (-4) / (2 - 0) = (2 + 4) / 2 = 6/2 = 3 <==
slope of Q : using 2 points and slope formula : (y2 - y1) / (x2 - x1)
(0,2),(2,-4)
slope = (-4 - 2) / (2 - 0) = -6/2 = -3 <==
