xy≤1,当x=y=1时,达到最小值-搜答案-拍题作业网

1/X-1/Y=3分子分母同除以xy=(1/y-2-1/x)/(2/y+3-2/x)=(1*3-2)/(2*3+3)=1/9

(x-y)^3=x³--3x²y+3xy²-y³得-3x²y+3xy=²(x-y)^3-(x³-y³)原式=x(x&su

3x的平方y-【（2xy的平方-2（xy-3/2x的二平方y)+xy]+3xy的立方＝3x²y-(2xy²-2xy+3x²y+xy)+3xy²=3x²

[XY(2X-Y)的平方-(-XY的二次方)的二次方]除以8XY=[(2x-y)²-xy³]÷8=[（-2/3-1）²+1/3*1]÷8=（25/9+1/3）÷8=28/

简单啊就1啊再问：为什么再答：你把一带进去-3xy和3xy就抵消了啊所以式子里就不含xy项了啊

解3x²y-[2xy²-4(1/2xy-3/4x²y)+xy]+3xy²=3x²y-(2xy²-2xy+3x²y+xy)+3xy&

原式=d{[(x+y)(x-y)+2xy]x+[(x+y)(y-x)+2xy]=d{[(x+y)(x-y)+2xy]x-[(x+y)(x-y)-2xy]}=d*4xy当x=1,y=5时20d=0d=0

需要满足-2mxy-1/3xy=0即可由上式可得m=-1/6

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

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

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

=3x^2y-2xy^2+2(xy-3/2x^2y)-xy+3xy^2=3x^2y+xy^2+2xy-3x^2y-xy=xy+xy^2=3*(-1/3)+3*1/9=-2/3

1/x-1/y=5y-x=5xy(3x+5xy-3y)÷(x-3xy-y)=(-15xy+5xy)/(-5xy-3xy)=-10xy/(-8xy)=5/4

=(x-1)(y-1)=-0.01*0.03=-0.0003

假设x,y,z>0.那么由算数几何不等式推出sqrt[3]{xyz}=3*sqrt[3]{x/y/z*y/z/x*z/x/y}=3*sqrt[3]{1/xyz}.把(1)代入上式,就得到左边>=3*3

（1）当1\x-1\y=3时求2x+3xy-2y\x-2xy-y的值=(2/y+3-2/x)/(1/y-2-1/x)=(2×(-3)+3)/(-3-2)=-3/(-5)=3/5;（2）求代数式x四次方

1/x-1/y=2时(y-x)/xy=2y-x=2xy2x+3xy-2y/x-2xy-y=[3xy-2(y-x)]/[-2xy-(y-x)]=-xy/-4xy=1/4

2(xy-5xy的平方)-(3xy的平方-xy)＝2xy-10xy的平方-3xy的平方＋xy＝3xy-13xy的平方当x=-1,y=1时,原式＝-3＋13＝10

(x+y)(x-y)+（x-y）²-（x²-3xy）=x²-y²+x²-2xy+y²-x²+3xy=x²+xy=x(x+

(9x^2y-6xy^2)÷(-3xy)-【(4y^2-9x^2)/(-3x+2y)】=-3x+2y-【(2y-3x)（2y+3x）÷(-3x+2y)】=-3x+2y-2y-3x=-6x=-6×（-1