x+x+x+x+y=40 x+y= 13x=y=

x+x+x+x+y=40 x+y= 13x=y= y=x(x x-y/x-x+y/y-(x+y)(x-y)/y² y/x=2 化简 x / y(x+y) - y / x(x+y) = x(x+y)(x-y)-y(y+x)(y-x)=(x-y)( )填空 X+Y=40,(X*Y)/(X+Y)=7.5 x+x+x+x+y+y+y=56 推倒公式:(x+y)(x*x-3x+y*y)=x*x*x+y*y*y怎么做. x+x+x+y+y=6.4 y+y+y+x+x=7.1 怎么算? x+x+x+y=60 .x-y=4 二元函数f(x,y)=x+y/x-y,求f(y/x,x/y) x-y/x+y=(x-y)²/x²-y²（x≠y) （x+y-5)*（x+y-5)+（x-y+3)=0 x*x-y*y 已知:3x-5y=0,求x/y,x-y/y,x-y/x x+y/3+x-y/2=6 4(x+y)-2(x-y)=40 x+x=y+30 y-x=x-5 x>=1,x-y