Bonsoir,
1. A = (2x+1)²+(4x-7)(2x+1) = 4x²+4x+1+8x²+4x-14x-7 = 12x²-6x-6
2. A = (2x+1)²+(4x-7)(2x+1) = (2x+1)(2x+1)+(4x-7)(2x+1) = (2x+1)[(2x+1)+(4x-7)] = (2x+1)[2x+1+4x-7] = (2x+1)(6x-6)
3. (2x+1)(6x+6) = 0
2x+1 = 0 ou 6x+6 = 0
2x = -1 ou 6x = -6
x = -1/2 ou x = -6/6
x = -1/2 ou x = -1
4. 82-(12-5x)² = 1
81-(12-5x)² = 0
9²-(12-5x)² = 0
(9-(12-5x))(9+(12-5x)) = 0
(9-12+5x)(9+12-5x) = 0
(5x-3)(21-5x) = 0
5x-3 = 0 ou 21-5x = 0
5x = 3 ou 5x = 21
x = 3/2 ou x = 21/5
