bonsoir
exo2:
montrer que (x-3)^2-9=x^2-6x
(x-3)^2-9=(x-3)^2 - 3^2 = (x-3+3)(x-3-3)=x(x-6)=x^2-6x
2)
A= x^2-6x+-7= (x-3)^2-9 - 7= (x-3)^2 - 16
3)
on utilise l'identite remarquable : a^2 - b^2 = (a+b)(a-b) »» (x-3)^2 - 4^2 = (x-3-4)(x-3+4)=(x-7)(x+1)
4)
B= x^2-4x-12 = x^2+2x-6x-12= x(x+2)-6(x+2)=(x+2)(x-6)
C= 4x^2-4x-8= 4(x^2-x-2)=4(x^2+x-2x-2)=4(x(x+1)-2(x+1))=4(x+1)(x-2)
