(1).x^2-8xy+7y^2(2).4x^2+9xy+2y^2(3).2x^2+7xy+3y^2(4).6x^2+xy-2y^2

7x^2y-[xy+4(xy^2+1/8xy)-3x^2y]答对给分 因式分解:8(x-2y)-x(7x+y)+xy. 1、(-7x^y)(2x^y-3xy^3+xy) 2、((x-y)^6)/((y-x)^3)/(x-y) .(x+y-2)(x+y-2xy)+(xy-1)^2 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 (x+y)(x+y+2xy)+(xy+1)(xy-1)(x+y)(x-y)+4(y-1) 化简：3x^2-[5xy-(x^y-3xy)+4x^2y-8xy] 2 3 2 3 2 3 2x y+(-4x y)-(-3x y) 2 2 (3x+x-5)-(4-x+7x) 2 2 (8xy-3y)-5xy-2(3xy-2x)12 2 2 2 __ 5(3x y-xy)-(xy-3x y)其中x=2 y=-1算出来 计算3xy[2xy-x(y-2)+x-1] 化简求值x-4y/2x-7xy+3y×x-2xy-3y/2x+3xy-2y÷3x-6y/4x-4xy+y,其中：x=1999,y=-1 {(x-y/x^2-2xy+y^2)-(xy+y^2/x^2-y^2)}*(xy/y-1) (1).x^2-8xy+7y^2(2).4x^2+9xy+2y^2(3).2x^2+7xy+3y^2(4).6x^2+xy-2y^2 x+y=8,xy=-2,求(5xy+4x+7y)+(6x-3xy)-(4xy-3y)的值 xy/3x+2y=1/8 xy/2x+3y=1/7这是一个方程组， 解方程组xy/3x+2y=1/8, xy/2x+3y=1/7 1.（xy-1）^2-(x+y-2xy)(2-x-y)2.(x+y)(x+y+2xy)+(xy-1)(xy+1) 因式分解xy(xy+2)+6(xy+8)-4(x+y-2)^2-16(x+y+1)谢谢 [-xy^2(2x+y)-8xy)-x^2y)]除以2xy=计算