x²-y²/x²-(y-z)²÷x²+2xy+y²/(x-y
若x-y=6,xy=-8,求代数式(x+y+z)²+(x-y-z)(x-y+z)-2·z(x+y)的值
x²/xy-x/y
急![(3x+y)²-3(3x-y)(x+y)-(x-3y)(x+3y)]÷(2xy)
x-y/x²÷x²-2xy+y²/xy*(xy-x²)
化简:[(x+y)²-(x-y)²]÷2xy
【(1)/(x-y)+(1)/(x-y)】÷(2x)/(x²-2xy+y²)
计算:(xy-x²)×x-y/xy
化简x-y分之x + x³-2x²y+xy²分之y³ ÷ y²-x
已知x/y=2,求2x(x+y)-y(x+y)/4x²-4xy+y²
f(x+y,xy)=x²+y²,则f﹙x,y﹚=?函数z=2xy-3x²-3y²
[-xy/(x-y)²]²×(y²-xy/x)³
x/xy-y²与y/x²-xy 通分