y=x(x

[x(x-y)-y(x-y)+(x+y)(x-y)]÷2x其中x=2012 y=2013 二元函数f(x,y)=x+y/x-y,求f(y/x,x/y) y=(lnX)/x-x (lim) x/x-y= x+y=5; x^y+y^x=17 因式分解下列式子：x(x-y)+y(y-x)=? y=x+x^x求导 x-y+5x-4x= ? y=(x^2+x)/(x+1) y=x+e^x,x y=x+4/x (x y=x^x（x>0)求导