3x^2-8xy-3y^2 10x 10y k=0-搜答案-拍题作业网

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原式=x²-y²-(4x²y²+12xy²+9y²)=x²-y²-4x²y²-12xy²-

xy(xy+1)+(xy+3)-2(x+y+1/2)-(x+y-1)^2=xy(xy+1)+(xy+1)+2-2(x+y)-1-[(x+y)^2-2(x+y)+1]=(xy+1)^2+2-2(x+y)

x^2-xy-6y^2+3xy+y+2

3xy是3x原式=(x-3y)(x+2y)+3x+y+2十字相乘x-3y2×x+2y1所以原式=(x-3y+2)(x+2y+1)

3xy[2xy-x(y-2)+x-1]=3xy(2xy-xy+2x+x-1)=3xy(xy+3x-1)=3x^2y^2+9x^2y-3xy

3xy[2xy-x（y-2）+x]＝3xy[2xy-xy+2x+x]=3xy(xy+3x)=3x²y²+9x²y

(-3x^y+2xy)-(4x^+xy)=-3x^y+2xy-4x^-xy=-3x^y+xy-4x^所以填上-3x^y+xy-4x^

(8xy-3x平方)-5xy-2(3xy-2x平方)=8xy-3x²-5xy-6xy+4x²=x²-3xy=4+6=10

1/x+1/y=(x+y)/xy=8x+y=8xy2x-3xy+2y/x+2xy+y=[2(x+y)-3xy]/[(x+y)+2xy]=(16xy-3xy)/(8xy+2xy)=13xy/10xy=1

-4x²y-8xy²+2x²y-3xy²=-2x²y-11xy²=-xy(2x+11y)

1、已知2x²+xy=10,3y²+2xy=6,求4x²+8xy+9y²的值为?分析：通过观察,可以把8xy拆成2xy+6xy,分别于剩余的两项组合,并提取公因

x^3y(-4y)^2+(-7xy)^2*(-xy)-5xy^3*(-3x)^2=16x^3y^3-49x^3y^3-45^3y^3=-78x^3y^3如果本题有什么不明白可以追问,

解3x²y+6xy-4x-8=(3x²y-4x)+(6xy-8)=x(3xy-4)+2(3xy-4)=(x+2)(3xy-4)

原式(-xy/3)²*[xy(2x-y)-2x(xy-y²)]=(x²y²/9)(2x²y-xy²-2x²y+2xy²)

设X=kY.kY^2/(3k+2)Y=1/8kY^2/((2k+3)Y=1/7由上式得：3k+2=8kY,2k+3=7kY所以2/（8Y-3）=3/（7Y-2）所以Y=1/2,X=1

∵x-y=4xy，∴2x+3xy-2yx-2xy-y=2(x-y)+3xyx-y-2xy=8xy+3xy4xy-2xy=112．故答案为：112．

(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

原式=3x(x-2y)-4(x-2y)=(x-2y)(3x-4)

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

（1）-3X^-2XY-8XY-(-5Y^2)-2X^2-Y^2=-3x^2-2xy-8xy+5y^2-2x^2-y^2=-5x^2-10xy+4y^2（2）3(-2+3X-X^2)-(4-3X+X^