x^2-3xy=-5.xy+y^2=3.求 x^2-2xy+y^2的值

x^2-3xy=-5.xy+y^2=3.求 x^2-2xy+y^2的值 已知xy为正整数,3xy=2x+3y+5.求xy=? （-3x^y+2xy)-( )=4x^+xy 当x-y=2xy时,求4x-3xy-4y/xy 由已知x+y=-2,xy=3那么2(x+xy)-[(xy-3y)-x]-(-xy)等于多少? ( )*3xy=6x^2y+2xy^2 2xy+5y^2+( )=x^2+3xy ( )-(x^2+3xy)=-xy-1/3y^2 3X^2+XY+Y=15 求XY. 已知x^2-xy=5,xy-y^2=-3求3(x^2-xy)-xy+y^2 已知：x+y=-2,xy=3.求:2(xy-3x)-3((2y-xy)的值 已知xy^2=-2,求-xy（x^2y^5-xy^3-y)的值. 已知xy^2=-2 求-xy(x^2y^5-xy^3-y) 已知xy^2=-2xy(x^2y^5-xy^3-y) xy^2=-3,求-xy(x^2y^5-xy^3-y) x*x+xy=3,xy+y*y=2,则x*x+2xy+y*y=________? 已知x:y=3:2,求(x²+3xy)/(xy+2xy) 已知1/x-1/y=2,求3x+7xy-3y/2x-3xy-2y答案是1/x-1/y=2(y-x)/xy=2 得：x-y=-2xy(3x+7xy-3y)/(2x-3xy-2y)=[3(x-y)+7xy]/[2(x-y)-3xy]=(-6xy+7xy)/(-4xy-3xy)=xy/(-7xy)=-1/7 谁能帮我解释一下=[3(x-y)+7xy]/[2(x-y)-3xy]=(-6xy+7xy)/(-4xy-3xy) 是怎