(1)2x^2+6xy-10y (2)4x^3-12x^2-18x (3)-7ab-14abx+49aby (4)5x(a+b-c)-10y(a+b-c) (5)πR^2-4πr^2

1-2/x+y=xy,4y+6x=xy.求xy的解? 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) 4xy-[(x²+5xy-y²)-(3xy-1/2y)]x=3,y=-6 xy-2{xy-[3x^2y-(4xy^2+0.5xy)]+4x^2y}+6xy^2 （X-3xy+4xy-y）-[-2x-2（xy-3/2xy）-y]+6xy的过程 1.已知x+y=-4,xy=3,求5（2分之1xy+2y）+[6x-(2xy+y-3x)]的值2.已知（x+3）^2+|x-y+10|=0求代数式5x^2y-[2x^2y-(3xy-xy^2)-3x^2]-2xy^2-y^2的值 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 因式分解 x-xy+3y-3x 2x+xy-y-4x+5y-6 5x^3y*(-3y)^2+(-6xy)^2*(-xy)+xy^3*(-4x^2) XY(XY+3)+(XY+4)+4(X+Y+1)-(X+Y+2) 分解因式：(1):2x^2+xy-6y^2-x-16y-10 (2):x^2-4xy+4y^2+x-2y-6 [(xy+2)(xy-2)-2x^2y^2+4]/xy,其中x=10,y=-1/25 [(xy+2)(xy-2)-2x^2y^2+4]/xy,其中x=10,y=-1/25 因式分解xy(xy+2)+6(xy+8)-4(x+y-2)^2-16(x+y+1)谢谢 已知1/x - 1/y = 2,求3x+7xy-3y / 2x-3xy-2y的值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)=-1/71/x-1/y=2到(y-x)/xy=2 是怎么变化的.. 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