x-y=98 xy=200 x/y=50 x=?y=?liu xia shu xue ji suan

|x|/x+y/|y|+xy/|xy|= 化简:(x+y-4xy/x+y)*(x-y-4xy/x-y)= 证明|xy|=|x||y| xy-(x+y)=1000 证明|xy|=|x||y| 已知：x(x-50y)+xy=50y^2,求：(x-y):y=? y'-xy=x/y通解 xy=y'ln(y'/x) 解方程x*x+xy=y+y*y 1/x-1/y=x,求5y+xy-5y/y-xy-x=? f(xy,x-y)=x^2+y^2+xy;f(x,y)/∂x;f(x,y)/∂y f(x,y)=xy+e^x x arctanx/y ,求f(x+y,x-y) sin(x*x+y)=xy 求y'x x*x+xy=3,xy+y*y=2,则x*x+2xy+y*y=________? X+X+Y+Y+Y=56,X+X+X+Y+Y=54.X=?Y=?XY=? [(y*y*y-y)/(xy+1)*(xy+1)-(x+y)*(x+y)]/[(x+y)*y/(x+1)]其中x=-11,y=1/12,化简再求值. 计算：( 根号xy-xy/x+根号xy)÷根号xy-y/x-y= X+Y=50 XY=616 求XY