18x/34y=9/1 x/y=?/?

18x/34y=9/1 x/y=?/? 先化简再求值 x(9x-y)-y(y-x)+(x-y)的平方,其中x=-1,y=2 x-y/x-x+y/y-(x+y)(x-y)/y² y/x=2 y'/y=1/x 化简 x / y(x+y) - y / x(x+y) = y'-(1/x)y=xe^-x 9y=3x-(x-1),4(x+y)-(2x+4)=8y 已知y/x=9/10则(1-y/x)[x/(y-x)]? x>0 y>0 x+y=1,4/X+9/y最小值x>0 y>0 x+y=1,求4/X+9/y最小值 x(x+y)(x-y)-y(y+x)(y-x)=(x-y)( )填空 y(x+y)+(x-y)²-（x+y）（x-y）,其中x=-1/3,y=3 （x-y)(x+y)-(x+y)^2+2y(y-x),其中x=1,y=3. 2y(x+二分之一y)-[(x+y)(x-y)+2y(y+x)],其中|x-1|=2 x+(9-8-y)=10 y+y-(9-8-y)=2 x-y=xx-9.9x xy=11y-1 y=? x=? x+y-xy=?x+(9-8-y)=10y+y-(9-8-y)=2x-y=xx-9.9xxy=11y-1 y=?x=?x+y-xy=? x>=1,x-y y=x-1(x 1.2x+9y=34 2.9x+4y 已知x+y=a,2x-y=-2a,求[（x/y-y/x)/(x+y)-x(1/x-1/y)]/[(x+1)/y]的值