若_x2 3x y 5=0,求x y的最小值

即x=y=1xy=1对不对?如果对的话x^2+2y^2-2xy-2y+1=0化简为你做的很对.就是这样解的,没有其他更好的方法了.这里用到的是数学里的

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

xy-12=4x+y≥2√(4xy)=4√(xy)xy-4√(xy)-12≥0(√(xy)-6)(√(xy)+2)≥0√(xy)≤-2,√(xy)≥6因为√(xy)≥0所以√(xy)≥6xy≥36所以

题目不很清楚哈,我理解是：已知：x-(xy)^0.5-2y=0;求：（2x-(xy)^0.5)/(y+2*(xy)^0.5);由已知：（x/y)-(x/y)^0.5-2=0;[(X/y)^0.5-2]

(x+1)^2+|y-1|=0(x+1)^2>=0|y-1|>=0x+1=0,y-1=0x=-1,y=12(xy-5xy的平方)-(3xy的平方-xy)=2xy-10xy^2-3xy^2+xy=3xy

这个是原题要求的吧|x|/x+|y|/y+|xy|/xy（1）xy>0x,y都大于零或都小于零x,y都大于零时|x|/x+|y|/y+|xy|/xy=|x|/x+|y|/y+|xy|/xy=x/x+y

2x+y=0y=-2x所以（y²-xy）/(x²+2xy）=（4x²+2x²）/(x²-4x²）=6x²/(-3x²）=

(3xy+2)^2+|7-x-y|=0,则3xy+2=0,7-x-y=0,即x+y=7,xy=-2/3(5xy+10y)-[-5x-(4xy-2y+3x)]=5xy+10y-(-5x-4xy+2y-3

x+2y=0,xy不等于0∴x=-2yx²+2xy/xy+y²=(4y²-4y²)/(-2y²+y²)=0

因为x+2y=0所以x=-2yxy=(-2y)*y=-2y^2xy+y^2分之x^2-2xy=-y^2分之4y^2+4y^2=-1/8

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

x+2y=0x=-2yxy+y^2分之x^2+3xy=x^2+3xy/xy+y^2=4y^2-6y^2/-2y^2+y^2=-2y^2/-y^2=2

若x+2y=0,xy不等于0,求分式xy+y^2分之x^2+2xy的值x+2y=0,x=-2yx^2+2xy/xy+y^2=(4y^2-4y^2)/xy+y^2=0

3/5再问：详细过程呢再答：y-x=3xyx-y=-3xy代入得：(-6xy+3xy)/(-3xy-2xy)=-3/-5=3/5

x-1的绝对值+（y+3）²=0x-1=0,y+3=0x=1,y=-31-xy-xy²=1+3-9=-5

再答：采纳一下，好吗？谢谢了再问：可是答案上的结果是0或负一哦再答：-1显然是错误的

x-√(xy)-2y=(√x-2√y)(√x+√y)=0因为x>0,y>0所以√x+√y>0所以√x=2√yx=4y2x=8y,√(xy)=2√y*√y=2y原式=(8y-2y)÷(y+4y)=6y/

因为x>0,y>0,所以将x-根号xy-2y=0因式分解得(根号x-2根号y)(根号x+根号y)=0所以根号x=2根号y,即x=4y后面请自己代入吧,我看不懂你的表述.不好意思了

x+y=5xy（2x-3xy+2y)/(x+2xy+y）=[2（x+y）-3xy]/[(x+y)+2xy]=(2×5xy-3xy)/(5xy+2xy)=7xy/7xy=1再问：若x＋1/x＝3,求(x

x²-7xy+12y²=0(x-3y)(x-4y)=0x1=3yx2=4yx=3y时原式＝9y²-3y²+y²/6y²=7/6x=4y时原式