9x+y=580 x+9y=420 怎么解

9x+y=580 x+9y=420 怎么解 x y=5 x-y=9怎么解 x+y=5 x-y=9怎么解 x+10y+9=10x+y怎么解 y+10x=x+y+9 10y+x=y+10x+27怎么做?六年级方程组！ x+x+x+y+y=6.4 y+y+y+x+x=7.1 怎么算? y/(x+y)-x/(x-y)=?怎么算? 推倒公式:(x+y)(x*x-3x+y*y)=x*x*x+y*y*y怎么做. 3x+2=y 5x+4=y 7x+6=y 9x+8=y 11x=y怎么解 x+9y=84 怎么解 4(x-y)-3(x-y)=9 5(x-y)+2(x-y)=11 y+10x=x+y+9 10y+x=y+10x+27 3(x+y)-2(x-y)=11 4(x+y)+3(x-y)=9 f(x,y)=x*x*x+y*y*y-9xy+27极值 x+y=9,3(x+y)+2x=33 怎么解 先化简再求值 x(9x-y)-y(y-x)+(x-y)的平方,其中x=-1,y=2 怎么求函数 y=x+9/x的反函数? x-y/x-x+y/y-(x+y)(x-y)/y² y/x=2