E = (2x-5)² -(2x-5)(x-8)
= (2x-5)(2x-5)-(x-8)
= (2x-5)(2x-5-x+8)
= (2x-5)(x+3)
pour x = -3
E =( -6-5)(-3+3)
E -1 x 0 = 0
pour x = 2/3
E = (4/3-5)(2/3+3)
E = 4/3 -15/3 x 2/3 + 9/3
E = -11/3 x 11/3 = -121/9
(2x-5)(x+3) = 0
soit 2x-5 = 0 donc 2x = 5 et x = 5/2
ou x+3 = 0 et x = -3