1/4x^3*(-2xy^2)+(-2x^2y)*(-1/2xy)*3xyz a(a^2+ab+b^2)+b(a^2+ab+b^2)

XY(XY+3)+(XY+4)+4(X+Y+1)-(X+Y+2) 整式乘法..1.3xy（x²y-xy²+xy）-xy²（2x²-xy+2x）2.（x-1）（x²-4x+3）-x（x²-5x+2) 3xy(x^2-xy^2+xy)-xy^2(2x^2-xy+2x) -3(2x^2-xy)+4(x^2+xy-6) 1-(3xy-x)+【-2(2x+3xy)】 计算3xy[2xy-x(y-2)+x-1] （-3x^y+2xy)-( )=4x^+xy 4(x²+xy-6)-3(2x²-xy) -3(2x²-xy)+4(x²+xy-6) -3(2x-xy)-4(-6+xy+x.其中x=1,y=-1 化简：3x^2-[5xy-(x^y-3xy)+4x^2y-8xy] 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^3+3x^2-2xy^2+1)+(-xy^2+x^2-2X^3+2)+(x^3-4x^2*y+3xy^2-8)= 已知x y=1,xy=-3,求2xy-4x 4(y-2(xy-x)) 分解因式（x^2+3x+2)(3+8x+4x^2)-90xy(xy+1)+(xy+3)-2(x+y+0.5)-(x+y-1)^2 若x-y=4,xy=1,求(-2xy+2x+3y)-(3xy+2y-2x)-(x+4y+xy)的值 (-2xy+2x+5y)-(3xy+2y-2x)-(x+4y+xy)其中x-y=4xy=-1 x-y=1,xy=2.求：(-2xy+2x+3y)-(3xy+2y-2x)-(x+4y+xy)的值