CORRECTION 3) Factoriser en reconnaissant un produit remarquable :
Factoriser les expressions suivantes : A(x) = 9 x2– 12 x+4
= (3 x)2−2×3 x×2+22 = (3 x−2)2
B(x) = 25 x2+20 x+4 = (5 x)2+2×5 x×2+22 = (5 x+2)2
C(x) = 4 x2+4 x+1
= (2 x)2+2×2 x×1+12 = (2 x+1)2
D(x) = 16 x2– 8 x+1
= (4 x)2−2×4 x×1+12 = (4 x−1)2
E(x) = x2– 9 = x2−32
= (x−3)(x+3)
F(x) = 16 x2– 25 = (4 x)2−52 = (4 x−5)(4 x+5)
G(x) = 49 x2– 1 = (7 x)2−12 = (7 x−1)(7 x+1)
