XY=X (X*1.45*65)怎么解-搜答案-拍题作业网

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

[2x(x²y-xy²)+xy(xy-x²)]/x²y=[2x^3y-2x^2y^2+x^2y^2-x^3y]/x²y=x-y=4

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

对.前提是x不等于y

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

X-Y=5,XY=3.XY是多少?

Y=X-5XY=X²-5X=3X²-5X-3=0X=(5±√37)/2Y=X-5X=(5-√37)/2,Y=(-5-√37)/2X=(5+√37)/2,Y=(-5+√37)/2

这题少括号了吧.

由题设可知y=xy-1，∴x=yx3y=x4y-1，∴4y-1=1，故y=12，∴12x=x，解得x=4，于是x+y=4+12=92．故答案为：92．

（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

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

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

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

[3xy(1-x)-6xy(x-1/2)]*2x*(-xy)平方=(3xy-3x²y-6x²y+3xy)(2x³y²)=12x^4y³-18x^5y&

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

limsin(xy)/x(x.y)->(0.2)=lim{[sin(xy)/xy]*y}=im[sin(xy)/xy]*(limy)(x.y)->(0.2)=1*2=2这里把(xy)看作一个整体,当(

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

xy+x=20 xy+y=18

由题意得：X＝Y+2.那么Y（Y+2）+Y+2＝20（Y+2）×（Y+1)=20所以y＝3那么x＝5可待入xy+y=18就不对了.（Y+2）×（Y+1)=20,Y应该是-6,X是-4,答案就对了.X＝

x²+xy=12 xy+y²=13

两式相加得到x+y=5,相减得y-x=1/5,故x=12/5,y=13/5xy=156/25,因为要求的都是正数,而且xy同正负,所以只考虑x,y正数即可故x²+y²=（x+y）^

X+y=3 xy=-5 Xy=?

X+y=3xy=-5X-y=?(x-y)^2=(X+y)^2-4xy=9+20=29则x-y=±根号29

由xy+x=16,得x=16/(y+1)代入xy-x=8,得16y/(y+1)-16/(y+1)=8=>16(y-1)/(y+1)=8=>(y-1)/(y+1)=1/2移项,通分得y-3/2(y+1)