(x-y)(x+xy+y)+xy(y-x) 其中x=7.1 y=2.92x+y=0,2x-y=0.5,求2x^2-1/2y^2

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(x-y)(x+xy+y)+xy(y-x) 其中x=7.1 y=2.92x+y=0,2x-y=0.5,求2x^2-1/2y^2
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(x-y)(x+xy+y)+xy(y-x) 其中x=7.1 y=2.92x+y=0,2x-y=0.5,求2x^2-1/2y^2
(x-y)(x+xy+y)+xy(y-x) 其中x=7.1 y=2.9
2x+y=0,2x-y=0.5,求2x^2-1/2y^2

(x-y)(x+xy+y)+xy(y-x) 其中x=7.1 y=2.92x+y=0,2x-y=0.5,求2x^2-1/2y^2
1.
(x-y)(x+xy+y)+xy(y-x)
=(x-y)(x+xy+y-xy)
=(x-y)(x+y)
=(7.1-2.9)*(7.1+2.9)
=10*4.2
=42
2.
2x+y=0 (1)
2x-y=0.5 (2)
(1)+(2)得：
4x=0.5
x=0.125=1/8
y=-0.25=-1/4
2x²-y²/2
=1/32-1/32
=0

|x|/x+y/|y|+xy/|xy|= -x-3xy+y xy-1+x-y 集合{(x,y)|xy xy(x-y)-x(x-y)² 【x(xy-xy)-y(x-xy)】÷3xy 计算：(xy-x²)×x-y/xy 【xy-x²】*xy/x-y （x^2+xy/x-y)/（xy/x-y)计算 化简x^-y^/x^-2xy+y^ (-x-y)(x^2+xy+y^2) 2*(x-y)²(y-x)(xy) XY（XY-X2)乘以------------X-Y x^2-xy/xy-y^2约分 (xy+1)(x+1)(y+1)+xy (xy+1)(x+1)(y+1)+xy 化简4xy-y-xy+x (xy+1)(x+1)(y+1)+xy