化简再求值[(x²+y²）²-4x²y²]÷(x²-y²）

题目

化简再求值[(x²+y²）²-4x²y²]÷(x²-y²）
其实,x=2,y=2/3.

答案

原式=(x^4+2x²y²+y^4-4x²y²)/(x²-y²)=(x^4-2x²y²+y^4)/(x²-y²)=(x²-y²)²/(x²-y²)=x²-y²=4-4/9=32/9