(x+1)³-(x-1)³=x(6x+2) (x+1-x+1)((x+1)²+2(x+1)(x-1)+(x-1)²)=6x²+2x 2(x²+2x+1+2x²-2+x²-2x+1)=6x²+2x 8x²-6x²-2x=0 2x²-2x=0 x(x-1)=0 x₁=0 x₂=1