résoudre l'équation 2(x+1)² - x²-1 = 0

2(x+1)² - x²-1 = 0
2(x+1)² - (x-1)(x+1) = 0
(x+1)(2x+2 -x+1) =0
(x+1)(x+3) = 0

x+ 1  =0                             x+3 =0
x = -1                                 x = -3

donc solution (-1; -3)