a) 9x²-(x+7)²
= 9x^2 - x^2 + 14x + 49
= 8x^2 + 14x + 49
b) (x+2)(x-5)-(x-5)(2x+1)
= [x^2 - 5x + 2x - 10] - [2x^2 + x - 10x - 5]
= x^2 - 3x - 10 - 2x^2 + 9x + 5
= -x^2 + 6x - 5
c) (2x+3)(x+2)+x+2
= 2x^2 + 4x + 3x + 6 + x + 2
= 2x^2 + 8x +8
J’espère t’avoir aidé ;)