化解求值：{（xy-y*）（x+1）-（y-1）（x*-y*)}(x+y*).*是指乘号,x=4/7y=2/5.要过程,速度急要.错了,米字符号指2平方

Question

化解求值：{（xy-y*）（x+1）-（y-1）（x*-y*)}(x+y*).*是指乘号,x=4/7 y=2/5.要过程,速度急要. 错了,米字符号指2平方

Answer 1

[（xy-y²）（x+1）-（y-1）（x²-y²)](x+y²)
=[y（x-y）（x+1）-（y-1）（x+y)(x-y)](x+y²)
=(x-y)[y(x+1）-（y-1)(x+y)](x+y²)
=(x-y)[xy+y-（xy+y²-x-y)](x+y²)
=(x-y)[xy+y-xy-y²+x+y](x+y²)
=(x-y)(x-y²+2y)(x+y²)
代入x=4/7 y=2/5得
原式
=(4/7-2/5)×(4/7-4/25+2×2/5)×(4/7+4/25)
=6/35×212/175×128/175
=(6×212×128)/(35×175×175)
=162816/1071875