B=2*(x-1)+2(x-1)(x+3)

Bonsoir


2(x-1)+ 2(x-1)(x+3)

Factorisons
2(x-1)+ 2(x-1)(x+3)
(x-1)[(2+2(x+3)]
(x-1)(2+2x+6)
(x-1)(2x+8)

Développons
2(x-1)+ 2(x-1)(x+3)
2x - 2 + 2(x² + 3x - x - 3)
2x - 2 + 2x² + 6x - 2x - 6
2x² + 6x - 8

2(x-1)+2(x-1)(x+3)
= 2x-2+2(x^2+3x-x-3)
= 2x-2+2x^2+6x-2x-6
= 2x^2 + 6x - 8