①6(x-y)-7(x y)=21;. ②2(x-y)-5(x y)=-1

x/2=y/3x=2y/3所以x²-2xy-3y²/x²-6xy-7y²=(x+y)(x-3y)/(x+y)(x-7y)=(x-3y)/(x-7y)=(2y/3

xy^2=-6(xy^2)^2=(-6)^2即x^2y^4=36(xy^2)^3=(-6)^3即x^3y^6=-216-xy(x^3y^7-3x^2y^5-y)=-xy[(x^3y^6)*y-3(x^

因为x/y=2所以x=2y是[x^2-xy+3y^2]/[x^2+xy+6y^2]吧=(4y^2-2y^2+3y^2)/(4y^2+2y^2+6y^2)=5y^2/12y^2=5/12

x^+2xy+y^+4=16(x+y)²=16-4=12(1)x^-2xy+y^=16(x-y)²=16(2)(1)-(2)2y*2x=-4xy=-1(3xy+6y^)+|x^-(

2x+3y-3xy+（4xy-3x）-（4y-7）=2x+3y-3xy+4xy-3x-4y+7=-x-y+xy+7=-6-6+2+7=-3

x=-1,y=-6或x=6,y=1代入式子得x^2-xy^2=37或30x^2y+xy^2=-42或42

题目是不是x^2y-7xy+6yx^2y-7xy+6y=y(x^2-7x+6)=y(x-1)(x-6)

x^2y+xy^2=xy（x+y）=7x6=42再问：��(x+1)^2=13��x^2+2x+3=再答：x^2+2x+3=（x+1）^2+2=13+2=15

（4xy+12y)+[7x-(3xy+4y-x)]=4xy+12y+7x-3xy-4y+x=xy+8x+8y=xy+8(x+y)=(-2)+8*3=-2+24=22

(5xy+4x+7y)+(6x-3xy)-(4xy-3y)=5xy+4x+7y+6x-3xy-4xy+3y=(5xy-3xy-4xy)+(4x+6x)+(7y+3y)=-2xy+10x+10y=-2x

-2x+6xy-2y/(7x+5y)-9xy-(3x+y)=[3(x+y)-x-y]/[7x+5y-9/2(x+y)-3x-y]=2(x+y)/[-1/2(x+y)]=-4

xy/x+y=6∴xy=6(x+y)3x-2xy+3y/-x+3xy-y=[3x-12(x+y)+3y]/[-x+18(x+y)-y]=-9(x+y)/17(x+y)=-9/17再问：你在啊？再答：在

∵A=8x²y-6xy²-3xy,B=7xy²-2xy+5x²y　∴C=3（A+B)　　=3(8x²y-6xy²-3xy+7xy²

那个2后面应该是y吧,直接化简呀,展开后得：2.5xy+10y+6x-2xy+y+5x=0.5xy+11x+11y=0.5xy+11(x+y)=0.5*14+11*(-7)=-70

原式=x^4y^8-3x³y^6-11.5xy²=(xy²)^4-3(xy²)³-11.5(xy²)=1296+648+69=2013

1、(-7x^y)(2x^y-3xy^3+xy)=-14x^(2y)+21x^(y+1)y^3-7x^(y+1)y;2、((x-y)^6)/((y-x)^3)/(x-y)=-(x-y)^3/(x-y)

已知x+xy=-2,xy-y=-6则X+Y=42x｛-4y-3[（x+xy）²+x]-½[（y-xy）²-2y]=2x｛-4y-3[（-2）²+x]-&fr

不会

原式=-x²y+2xy²+2x²y²-4xy³-3x³+27x³y-18x²y²+2x²y-18x&

因为,x-y=3xy所以：-3x+6xy+3y/[(7x-5y)-9xy-(3x-y)]=[-3(x-y)+6xy]/[(7x-5y)-9xy-(3x-y)]=[-3*3xy+6xy]/[7x-5y-