(1)
(x-1)(x+2)(x-3)(x+6)+9x²
=((x-1)(x+6))*((x+2)(x-3))+9x²
=(x²-6+5x)(x²-6-x)+9x²
=((x²-6)+5x)*((x²-6)-x))+9x²
=((x²-6)²+4x*(x²-6)-5x²)+9x²
=(x²-6)²+4x*(x²-6)+4x²
=(x²-6)²+2*2x*(x²-6)+(2x)²
=(x²-6+2x)²
(2)
因为x(x-1)-(x²-y)=-3
x²-x-x²+y=-3
-x+y=-3
x-y=3
x²+y²-2xy=
=（x-y)²
=9