已知X>0,Y>0,2X Y>3,求XY的最大值和相应值
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2x-3y=0所以y=2x/3代入(x^2+xy-y^2)/(2x^2+xy-y^2)得到[x^2+x*2x/3-(2x/3)^2]/[2x^2+x*2x/3-(2x/3)^2]=(x^2+2x^2/
2x^2-3xy+y^2=(2x-y)(x-y)=0则可得2x=y或x=y①当2x=y时把2x=y代入其中得x/y+y/x=x/2x+2x/x=1/2+2=2.5②当x=y时x/y+y/x=x/x+x
x²-5xy+6y²=0(x-2y)(x-3y)=0x=2y,x=3y所以x/y=2,x/y=3
(2x+y)/(x^2-2xy+y^2)X(x-y)=(2x+y)/(x-y)²*(x-y)=(2x+y)/(x-y)x-3y=0,x=3y(2x+y)/(x-y)=(6y+y)/(3y-y
x²+xy+1/4y²+3/4y²-3y+3=0(x+1/2y)²+3/4(y-2)²=0∴x+1/2y=0y-2=0∴x=-1y=2∴y^x=2^(
3x*+xy-2y*=0(3x-2y)(x+y)=0那么x=2y/3或x=-yy/x=3/2或x/y=-1(x/y)-(y/x)-(x*+y*)/(xy)=(x/y)-(y/x)-(x/y+y/x)=
由y=3xy+x得x-y=-3xy2x+5xy-2y/x-2xy-y=2(x-y)+5xy/x-y-2xy=-6xy+5xy/-3xy-2xy1/5
y-x-2xy=0y-x=2xyx-y=-2xy(3x+xy-3y)/(y-xy-x)=[3(x-y)+xy]/[(y-x)-xy]=(-6xy+xy)/(2xy-xy)=-5xy/xy=-5
答:x>0,y>0x-√(xy)-2y=0(√x-2√y)(√x+√y)=0因为:x>0,y>0所以:√x+√y>0所以:√x-2√y=0所以:√x=2√y所以:x=4y所以:[x+3√(xy)+2y
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×(
3x^2+xy-2y^2=0推出(3x-2y)(x+y)=0推出x=-y或x=(2/3)y{(x+y)/(x-y)+4xy/(y^2-x^2)}/{(x+3y)*(x-y)}/x^2-9y^2推出:{
x-2y=0x=2y所以xy=2y²x²=4y²所以原式=(4y²-6y²+y²)/(8y²+2y²-3y²)
y-x-2xy=0所以x-y=-2xyy-x=2xy所以原式=[3(x-y)+xy]\[(y-x)-xy]=[3×(-2xy)+xy]\(2xy-xy)=-5xy\xy=-5
3-y=0x+y=0∴x=-3y=3[2(x+y)-3(xy+4)]÷1/xy=[2×0-3(-9+4)]÷(-1/9)=15×(-9)=-135
①xy同非负时,2x-3√xy-2y=(2√x+√y)(√x-2√y)=0∴√x=2√y,x=4y②xy同负时,2x-3√xy-2y=[2√(-x)+√(-y)][√(-x)-2√(-y)]=0∴√(
2x+y+3=xy,①若x=1,则y不存在,此时5x+4y无最值;②若x≠1,则y=(2x+3)/(x-1),M=5x+4y=5x+(8x+12)/(x-1)=(5x²+3x+12)/(x-
2x-3√(xy)-2y=0(2√x+√y)(√x-2√y)=0因为x>0,xy≥0所以y≥02√x+√y>0所以√x-2√y=0,即x=4y(x^2+4xy-16y^2)/(x^2+xy-9y^2)
2X^2+3xy-2y^2=0(2x-y)(x+2y)=0即:2x-y=0或,x+2y=0y=2x或x=-2y当y=2x时:x+y/x-y=3x/(-x)=-3当x=-2y时:x+y/x-y=-y/(
∵x-y=4xy∴原式=[2(x-y)+3xy]/[-(x-y)-2xy]=(8xy+3xy)/(-4xy-2xy)=11xy/(-6xy)=-11/6