x y=2,xy=7求x三次方y-搜答案-拍题作业网

原式=2xy(x²+2xy+y²)=2xy(x+y)²=2*2*4²=64

A-B=x³+2y³-xy²-(-y³+x³+2xy²)=x³+2y³-xy²+y³-x³

/>根据非负数之和为0得x+1=02(y-2）=0解得x=-1y=2于是x³-3xy+y³=-1³-3×(-1)×2+2³=-1+6+8=13

x^3y-2x^2y^2+xy^3=x^3y+2x^2y^2+xy^3-4x^2y^2=xy(x^2+2xy+y^2)-4x^2y^2=xy(x+y)^2-4x^2y^2=12×7×7-4×12×12

x³y+2x²y²+xy³=xy(x²+2xy+y²)=xy(x+y)²=1×3²=9

xy的三次方-2x²y²+x的三次方y=xy(y²-2xy+x²)=xy(x-y)²

=xy(x²-2xy+y²)=xy(x-y)²=2*1²=2

x³y-2x²y+xy=xy(x²-2x+1)=xy(x-y)²=1/2×2²=2

∵x-y=-2,xy=-1/4∴-2x²y²+xy³+x³y=xy(x²-2xy+y²)=xy(x-y)²=-1/4*(-2)&#

(2x^4)y³－x³y^4=(x³y³)(2x－y)=(xy)³(2x－y)=4³×(1/16)=4

原式=xy(x²-2xy+y²)这一步就很清楚的明白是公式的运用了：a²-2ab+b²=(a-b)²所以=xy(x-y)²将x-y=-1,x

-xy(x²y的五次方-xy的三次方-y)=-x³y的6次方+x²y的4次方+xy²=-（xy²）³+（xy²）²+xy

由题可知,x+y+1=0,xy+3=0即得x+y=-1,xy=-3（x+y)²=x²+2xy+y²∴(-1)²=x²+2×（-3）+y²即x

解x-y=5两边平方x²-2xy+y²=25∵xy=3∴x²+y²=25+2xy=25+6=31∴x³y+xy³=xy(x²+y&

y-2x=-20102x-y=20102x^4y³-x³y^4=x³y³(2x-y)=(xy)³(2x-y)=10³×2010=201000

z=x^3+y^3+3xy∂z/∂x=3x^2+3y∂^2z/∂x^2=6x=A∂z/∂y=3y^2+3x∂^2z/

原式=-x³y^6+x²y^4+xy²=-(xy²)³+(xy²)²+(xy²)=-2³+2²+2=

m=x^2-3xy^2+2xy^2+3y^3,n=x^3-2x^2+xy^2-5y^3,则2x-7x^2*y^3+5xy^+14y^3等于多少?3m=3x^2-9xy^2+6xy^2+9y^3n=x^