(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? (x+y)(x+y+2xy)+(xy+1)(xy-1)(x+y)(x-y)+4(y-1) 因式分解 x-xy+3y-3x 2x+xy-y-4x+5y-6 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 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 1、(-7x^y)(2x^y-3xy^3+xy) 2、((x-y)^6)/((y-x)^3)/(x-y) 因式分解30题(要过程)am+an+bm+bn x^2+5y-xy-5x x2+xy+2xz+x (a+b)x-(b+a)y -12x(x-y)-(y-x)x^2 2x^2+4x+2 x(x+z)-y(y+z) 2(x^2-3ab)+x(4a-3b) 4x^2+12xy+9y^2-25 x^4-16 16x^4-1 x^2+9x+8 x^2-10xy+24y^2 2x^2+15xy-8y^2 3x^2-6xy+3y^2 24x^2+22x-21 -x^2+4xy- 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 分解因式：(1):2x^2+xy-6y^2-x-16y-10 (2):x^2-4xy+4y^2+x-2y-6 4xy-[(x²+5xy-y²)-(3xy-1/2y)]x=3,y=-6 -3(2x-xy)-4(-6+xy+x.其中x=1,y=-1 xy-2{xy-[3x^2y-(4xy^2+0.5xy)]+4x^2y}+6xy^2 x-y/x^2+xy除以xy-x^2/x^2y^2-x^4*1/x-y （X-3xy+4xy-y）-[-2x-2（xy-3/2xy）-y]+6xy的过程 已知x-y=6,xy=-1,求(2x+3x-2xy)-(x+4y+xy)-(3yx-2x+2y)的值 .(x+y-2)(x+y-2xy)+(xy-1)^2 5x^3y*(-3y)^2+(-6xy)^2*(-xy)+xy^3*(-4x^2) XY(XY+3)+(XY+4)+4(X+Y+1)-(X+Y+2)