0.5x+0.7y=35 x+0.4y=40

0.5x+0.7y=35,x+0.4y=40.求x=?,y=? 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 0.5x+0.7y=35 x+0.4y=40 x+x+y+y+y=21 ,x+x+y+y+y+y+y=27 ,x ,y=? x+x+y+y+y=21 ,x+x+y+y+y+y+y=27 ,x ,y=? y=x(x 已知X,Y独立,P(x)=0.5,p(x+y)=0.7,求p(y). 0.58=(0.5x+0.7y)/(x+y)求X比y怎么求 老师.0.58=(0.5x+0.7y)/(x+y)求X比y怎么求 x+x+x+x+y+y+y=56 （x+3y)²-2（x-y)（x+y)+(x+y)²其x=0.5,y=-2 x+x+x+y+y=6.4 y+y+y+x+x=7.1 怎么算? 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