[2x²-（x+y）（x-y）][（-x-y）（y-x）+2y²]
= [2x²-(x²-y²)][-(x+y)(-(x-y))+2y²] (一个负号提出来,再一个负号提出来,负负得正抵消)
=(2x²-x²+y²)(2y²+x²-y²)
=(x²+y²)(x²+y²)
=(x²+y²)²
=(1+4)²=25