5.已知:x+y= ,xy=1.求x³y+2x²y²+xy³的值.-搜答案-智慧作业帮

题目写错应该是求（6xy+7y)+[8x-(5xy-y+6x)]（6xy+7y)+[8x-(5xy-y+6x)]=6xy+7y+8x-5xy+y-6x=xy+2x+8y=xy+2(x+4y)=5+2×

x-xy=8(1)xy-y=-9(2)则有(1)-(2):X-XY-XY+Y=X+Y-2XY=8-(-9)=17

1、答案：负七分之五解题：xy=2x+2y代入原式,整理合并同类项即可得出2、如果只考虑在同一平面内,有三条线.如图

首先化简通分1/x+1/y=5得：（x+y)/xy=5即有x+y=5xy将要求的分式化简：3x+xy+3y/x-2xy+y=3x+3y+xy/x+y-2xy（根据加法交换律）=3（x+y)+xy/(x

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

原式=6xy+7y+8x-5xy+y-6x=xy+2x+8y=xy+2(x+4y)=···再问：还有些题哈……

原式=6xy+7y+8x-5xy+y-6x=xy+2(4y+x)=5-2=3

6xy+7y+[8x-5xy+y-6x]=6xy+7y+8x-5xy+y-6x=(6xy-5xy)+(7y+y)+(8x-6x)=xy+8y+2x=xy+2(4y+x)=5-2=3再问：请问x=？y＝

1.已知x+y=-4,xy=3,求5(xy/2+2y)+[6x-(2xy+y-3x)]的值5(xy/2+2y)+[6x-(2xy+y-3x)]=5xy/2+10y+6x-2xy-y+3x=xy/2+9

（1）∵xy+x=-1①，xy-y=-2②，∴①-②得x+y=1；（2）先把xy+x=-1，xy-y=-2的值代入代数式，得原式=-x-[2y-1+3x]+2[x+4]=-x-2y+1-3x+2x+8

2(x+xy)-[(xy-3y)-x]-(-xy)=2x+2xy-xy+3y+x+xy=3x+3y+2xy=3（x+y）+2xy=3*（-2）+2*3=0

x-y=9(x-y)²=9²x²-2xy+y²=81x²+y²=81+2xy=91所以(x+y)²=x²+y²

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

xy+1/xy>=2√（xy*1/xy）=2(当xy=1/xy即xy=1时取等号)x/y+y/x>=2√（x/y*y/x）=2(当x/y=y/x即x=y取等号)当x=y=1时可以同时满足两项的等号要求

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

那9是负的吗～如果不是等于负1,如果是负九等于十七～用第一个等式减第二个等式

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