若{5x+2y=14 2x+5y=21 则x+y=( ) x-y=( )
若3x-5y=0,则x+y/x=(),x-y/y=(),2x-3y/2x+3y=( )
已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y)
6(x-y)-2(x+y)=14 3(x-y)+(x+y)=5
已知x*x+4x+y*y-2y+5=0,则x*x+y*y=?
先化简再求值(x-y)(x+y)-(x-2y) 的完全平方+x(3x-5y)-(x-y)(x-2y),其中x=1/2 y
若(x*x+y*y)(x*x+y*y)-4x*x*y*y=0,求代数式(x*x+5xy+y*y)/(x*x+2xy+y*
分式的加减:[(x/y-y/x)除以(x+y)+x(1/y-1/x)]除以1+x/y,其中x=5,y=2
解方程组(x+y)(x-2y)=-5 (x-y)(x+2y)=7
3(x+y)-4(x-y)=11,2(x-y)+5(x+y)=27
若(x-y)/(x+y)=3 则(x+2y)/(6x-7y)等于
x-y / 5y= (y-x)^2 / ( )
若{5x+2y=14 2x+5y=21 则x+y=( ) x-y=( )