已知2x+3y=18 2x-y=2 则x=多少;y=多少

已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y) 已知2x=3y,则y分之x=< >,y分之x+y=< >. 已知x-y=3,求[（x+y)(x-y)-(x-y)^2+2y(x-y)]除以的值 已知3x =2y 求x/x+y+y/x-y-y²/x²-y² 已知f(x+y,y/x)=x^2-y^2,则f(x,y)= 比例线段：已知x/y=2/3,则 x/x+y= ,x-y/x+y= 要过程! 已知|x|=2,|y|=3,|x+y|=-(x+y)求x-y 已知|x+y-3|+(x-y)2=0则 已知方程组{(X+Y)-3(X-Y)=7,2(X+Y)+(X-Y）=-7}则(X+Y)(X-Y)= 已知2y-x=-3,求[4y(2x-y)-2x(2x-y)]/(2x-y 已知F(X+Y,X-Y)=X^2*Y+X*Y^2,则F(X,Y)=? 已知x*x+4x+y*y-2y+5=0,则x*x+y*y=? 已知x+2y=3则x=? x-y=7则y=? 已知x^2-3xy+2y^2=0 则x/y+x/y= 已知3x-4y=0,则x^2-y^2/x^2+y^2 已知(3x+y+6)²+|x+y+2|=2,则x=,y=. 已知x-2y=3,则(2x+y-6)/(3x-y-9)=? 已知2x-3y=0则3x-y比x+2y=