الاجابة
c(y2-1) = 2(y2-1)2 -4(y2-1) + 3
(y2-1)2 = (y2-1)(y2-1)
(y2-1)2 = y4 – 2y2 + 1
C(y2-1) = 2(y4-2y2+1) -4(y2-1) +3
C(y2-1) = 2y4 – 8y2 + 9