(x-1)²+(x+1)²=(x+2)²-2x+2 x²-2x+1+x²+2x+1=x²+4x+4-2x+2 2x²+2=x²+2x+6 x²-2x-4=0 D=4-4*(-4)=20 x1=(2+2√5)/2 x2=(2-2√5)/2