1.(x-y)(-x-y)(x²+y²)= - (x-y)(x+y)((x²+y²)= - (x²-y²)(x²+y²)= - x的四次方+y的四次方楼上的计算错误了,纠正下2.5（3-5a）²-5（3a-7）（3a+7）=5（3-5a）²-5...