1/x²+1/y²怎么化简成y²+x²/x²*y² 急用,说

1、y-x/x²-y² 因式分解:x²(x-y)+(y-x) 2.(x+y)²(x-y)²-(x-y)(x+y）(x²+y²) 已知x+y=1,xy=-二分之一,求x（x+y)(x-y)-x(x+y)² 已知x²+y²+5=2x+4y,求【2x²-(x-y)(x-y)】【(x+y-1)(x-y [(y-2x)(-2x-y)-4(x-2y)²]*2y,其中x=1,y=2 【(1)/(x-y)+(1)/(x-y)】÷(2x)/(x²-2xy+y²) 计算3x[xy-2x(1/y-x/3]+3y(x²-y²) 计算:1、(xy分之x²-y²)×(x-y分之x)-(y分之x)； 若|x+2y-1|+y²+4y+4=0,求（2x-y）²-2（2x-y)(x+2y)+(x+2y)& (2x-y)²-4(x-y)(x+2y) (x-y)³+9(x-y)-6(x-y)²