(9X+5Y)/(X+Y)=7.5,求X/Y=?

已知:3x-5y=0,求x/y,x-y/y,x-y/x (9X+5Y)/(X+Y)=7.5,求X/Y=? 已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y) 已知X.x+y.y-4x+2y+5=0,求4X.X-12X Y+9Y.y的值 求(X+Y)(X-Y)(X²+Y²),X=5 Y=2, (x-y)/(x+y)=3求( 3x-2y-1)/(x+y-5) 已知：4x = 5y,求(x+y) ：y x-y=9,x*y=5,求x^2+y^2的值 5x*2y=（x-y）^2 x+9y=55 求x、y 已知(x-y)(x-y-6)+9=0,且x+y=5,求x,y的值 {(x+y)/2+(x-y)/3=1,(x+y)-5(x-y)=2.求x=?,y=? |x|=3 |y|=5 |x-y|=|x|+|y| 求 X+Y和 X-Y 等于多少 已知x+y=-5,x*x+y*y=19求xy和（x-y)*(x-y)的值 二元函数f(x,y)=x+y/x-y,求f(y/x,x/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*y)的值 x+y+|x-y|=-56 求x*y 最小值 x^y=y^x,求dy. 求函数f（x,y）=x×x×x－y×y×y+3×x×x+3×y×y－9x的极值