∵x²-2x=-1/3x²-2x+1=-1/3+1∴(x-1)²=2/3(x-1)^2+(x+3)(x-3)+(x-3)(x-1)=(x-1)²+x²-9+x²-4x+3=(x-1)²+2x²-4x+2-8=(x-1)²+2(x-1)²-8=3(x-1)²-8=3×(2/3)²-8=4/3-8=-20/3