Bonjour,
A= (x - 1) (2x + 3) + 4x (2x + 3)
1) Développer et réduire A
A = x × 2x + x × 3 - 1 × 2x - 1 × 3 + 4x × 2x + 4x × 3
A = 2x² + 3x - 2x - 3 + 8x² + 12x
A = 10x² + 13x - 3
2) Factoriser A :
A = (2x + 3)(x - 1 + 4x)
A = (2x + 3)(5x - 1)
3) Calculer A pour x = 2
A = (2 × 2 + 3)(5 × 2 - 1)
A = (4 + 3)(10 - 1)
A = 7 × 9
A = 63
