Bonsoir !
E = ((x-5)(x+1)+(x-5)(2x+3)
Développer et réduire :
E = x²+x-5x-5+2x²-3x-10x+15
E = 3x²-17x+10
Pour x = 1
E = 3*1²-17*1+10
E = 3-17+10
E = - 4
Factorisation :
E = (x-5)(x+1)+(x-5)(2x-3)
(x-5)(x+1+2x-3)
(x-5)(3x-2) = 0
(x-5) = 0 => x = 5
(3x-2) = 0 => x = 2/3
Bonne soirée.
