Question

先化简,再求值 （1）[(x-y)的平方+（x+y)(x-y)]÷2x 其中X=2010,y=2009 （2)y(x+y

Answer 1

1 [(x-y)²+(x+y)(x-y)]÷2x=(x²-2xy-y²+x²-y²)÷2x=(2x²-2xy)÷2x=x-y

2 y(x+y)+(x+y)(x-y)-x²=xy+y²+x²-y²-x²=xy

3 x²-（x-1)-x(x²+x-1)=x²-x+1-x³-x²+x=1-x³