+2y=1 xy+x=1 3x- =5 x2-2=3xxy=1 2x(y+1)=c 2x-y=1 x+y=0 的解谁知道

已知xy/x+y=1/2,则代数式3x-5xy+3y/-x+3xy-y= 若x-y=4,xy=1,则(2x+y-2xy)-(3x+2y+xy)-(4xy+3y-5x)= (-2xy+2x+5y)-(3xy+2y-2x)-(x+4y+xy)其中x-y=4xy=-1 若1/x-1/y=2,求3x-2xy-3y/x-xy-y的值3x-2xy-3y/x-xy-y 不好意思，是3x-2xy-3y/x-2xy-y 4xy-[(x²+5xy-y²)-(3xy-1/2y)]x=3,y=-6 先化简,再求值:{xy(x²-3y)+3xy²}(-2xy)+x³y²(2x-y),其中x=-1/2,y=-5 5xy平方-2x平方y+[3xy平方-(4xy-2x平方y-2x平方y)],其中x=-2,y=-1求值 【数学】已知 1/x-1/y=3 求 5x-xy-5y / x-2xy-y=?已知 1/x=1/y 求 2x-3xy-2y / x-2xy-y=? 已知1/x+1/y=5,求x+y+3xy/2x-4xy+2y的值,已知1/x+1/y=5,x+y+3xy/2x-4xy+2y的值, (5x²y-2xy²-3xy)-(2xy+5x²y-2xy²),x=-1/5,y=-1/3 （x+2y-3xy)-(-2x-y+xy),其中x+y=1/2,xy=-1/2 已知1/x=3+1/y,则(2x-5xy-2y)/(y+3xy-x)=_______. 已知1/x-1/y=-3,则x+5xy-y/3x-2xy-3y= 已知3/(x-y)=1/xy 求(-x-2xy+y)/ (2x+3xy-2y) 5(3x^y-xy^)-(xy^+3x^y),其中x=1/2y=-1 已知1/x+1/y=5 求2x-3xy+2y/3x+2xy+3y 已知1/x-1/y=5,求分式2x+5xy-2y/3x-xy-3y 已知1/x+1/y=1/2,求代数式3x-5xy+3y/-x+3xy-y