8 Les propositions suivantes sont-elles vraies ou fausses ? Cochez la bonne réponse. V a. (5-2y)2 = 10 - 20y + 4y2 b. (x-7)2 = (7 - x)? c. (9 + 3a) (9-3a) = 81-

A)Faux

(5-2y)^2

=(5×5)-(5×2y)+(2y×2y)-(2y×5)

=25-10y+4y^2-10y

=4y^2-20y+25

B)Vrai

(X-7)^2

=(x×x)-(x×7)+(7×7)-(7×x)

=x^2-7x+49-7x

=x^2-14x+49

(7-x)^2

=(7×7)-(7×x)+(x×x)-(x×7)

=49-7x+x^2-7x

=x^2-14x+49

C)Faux

(9+3a)(9-3a)

=(9×9)-(9×3a)+(3a×9)-(3a×3a)

=81-27a+27a-9a^2

=-9a^2+81

D)Faux

(X+11)^2

=(x×x)+(x×11)+(11×11)+(11×x)

=x^2+11x+121+11x

=x^2+22x+121

Distributivité