先化简,再求值x²(1-y)-x³y÷xy+(y+1)(y-1),其中

先化简,再求值x²(1-y)-x³y÷xy+(y+1)(y-1),其中
先化简,再求值x²(1-y)-x³y÷xy+(y+1)(y-1),其中

先化简,再求值x²(1-y)-x³y÷xy+(y+1)(y-1),其中
原式=x²-x²y-x²+y²-1=-x²y+y²-1
x=1/(√2-1)=(√2+1)/(√2-1)(√2+1)=√2+1
把x=√2+1,y=-2代入得
2(√2+1)²+4-1
=2(2+2√2+1)+3
=2(3+2√2)+3
=9+4√2