已知x y=3,xy=1,求代数式5xy 4x-搜答案-搜搜做题作业网

xy^2*(-x^2y^2)*（1/2xy^3)^2=xy^2*(-x^2y^2)*（1/4x²y^6)=xy^2*(x^4y^8)*(-1/4)=(-1/4)*xy²*(xy&#

令F（XY）=1/XY+XY,当XY=1的时候,F（XY)=2,最小.（可由函数图形象得出）.XY趋于正无穷大的时候F(XY)趋于正无穷大,XY无限趋于零的时候F(XY)趋于正无穷大.所以XY越接近1

-xy（x^2y^5-xy^3-y)=-(xy^2)^3+(xy^2)^2+xy^2=-(-2)^3+4-2=8+4-2=10

此题应该抄错了,应该是遗漏了一个x,∵xy/(x+y)=2∴1/x+1/y=1/2(3x-5xy+3y)/(-x+3xy-y)=(3x-5xy+3y)/(-x+3xy-y)[分子分母同除以xy,得]=

(-2xy+2x+3y)-(3xy+2y-2x)-(x+4y+xy)=-6xy+3x-3y=-6×(-2)+3×1=15

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

解(x+1)平方+/y-1/=0∴x+1=0,y-1=0∴x=-1,y=1∴2(xy-5xy平方)-(3xy平方-xy)=(2xy+xy)+(-10xy平方-3xy平方)=3xy-13xy平方=3×(

3xy-[2xy-2(xy-2分之3xy)+xy]+3xy=6xy-[2xy-2xy+3xy+xy)=6xy-4xy=2xy=2×3×3分之1=2

平方和绝对值都大于等于0相加等于0,若有一个大于0,则另一个小于0,不成立.所以两个都等于0所以x+1=0,y-1=0x=-1,y=1后面漏了平方吧原式=2xy-2xy²-3xy+xy&su

=5xy+2x-3y+2xy-5x=7xy-3x-3y=7xy-3(x+y)x+y=1,xy=-6代入7*（-6）-3*1=-45

答案是3/2你是不是把分母打错了教你个方法因为上下是齐次的直接令x=3y=2带入就行

代数式可化为2x+2xy-xy+3y+x+xy=3x+3y+2xy=3（x+y）+2xy=3×（-2）+6=0a^2-b^2=15 a^2-2ab+b^2=5&nbs

3/(x-y)=1/xyx-y=3xyy-z=-3xy原式=[(y-x)-2xy]/[2(x-y)+3xy]=[(-3xy)-2xy]/[2(3xy)+3xy]=-5xy/9xy=-5/9

3xy=2x+3y+5(3y-2)(x-1)=7所以3y-2=7x-1=1得y=3x=2xy=6或3y-2=1x-1=7得y=1x=6xy=6所以xy=6

16524

3(x^2-xy)-xy+y^2=3(x^2-xy)-(xy-y^2)=3*5-(-3)=15+3=18

原式=-xy²（x²y^4-xy²-1）∵xy²=-2原式=2（（-2)²-（-2）-1）=10

1.若将多项式X2+2KXY+X-15不含XY项,则K3-1=?∵多项式X2+2KXY+X-15不含XY项则k=0∴K3-1=-12.已知XY=-2,X-Y=3,求（X+Y）×（X-Y）-Y2+（X-

(-2xy+2x+3y)-(3xy+2y-2x)-(x+4y+xy)=-2xy+2x+3y-3xy-2y+2x-x-4y-xy=-6xy+3x-3y=-6*(-2)+3*1=15不懂可追问,有帮助请采