x y-3>0,x-y 1>0,x

2y+3x=2xy(2y+3x)/(2xy)=1(1/x)+(3/y)=11≥2√(3/(xy))1≥12/(xy)xy≥12xy的最小值是12

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)=

设y1=k1x^2,y2=k2/(x+3)y=y1-y2=k1x^2-k2/(x+3)因为-k2/3=2k2=-69k1+6/6=0k1=-1/9因此y=-x^2/9+6/(x+3),x不等于-3

绝对值大于等于0,相加等于0,若有一个大于0,则另一个小于0,不成立所以两个都等于0所以x+y+1=0xy+3=0xy=-3x+y=-1两边平方x^2+2xy+y^2=(-1)^2x^2+y^2=1-

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

直接降维呗y2=y1*u=xcosxuy'=(cosx-xsinx)u+xcosxu'y''=(-sinx-sinx-xcosx)u+(cosx-xsinx)u'+(cosx-xsinx)u'+xco

1)由题意有a^3x+1=a^（-2）x化简有(a^（-2）-a^3）x=1∵a＞0且a≠1,∴a^（-2）-a^3≠0∴当x=1/(a^（-2）-a^3)时,y1=y22)由题意,a^3x+1＞a^

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×(

设y1=k1xy2=k2/xy=y1+y2=k1x+k2/x将x=1时y=0与x=2时y=3带入此式则2k1+k2/2=3解方程组求k1和k2解得k1=2k2=-2k1+k2=0所以y与x的关系就是y

1、OA=t,OB=8/t,AC=k/t,BD=k*t/8四边形ODPC的面积=t*8/t-1/2*t*k/t-1/2*8/t*k*t/8=68-k=6k=2；2、k=3时,S有最大值；3、t>4时,

3x²+3xy=03x²=-3xy因为x不等于0所以x=-y所以x：y=1：-1

设Y1=k1xY2=k2xY=Y1+Y2=k1x+k2/x当X=1.Y=-3时...k1+k2=-3把XY代进去当X=2,Y=0时2k1+k2/2=0也就是4k1+k2=0所以k1=1k2=-4所以Y

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

x²-10x+25+|y-3|=0(x-5)²+|y-3|=0所以x=5,y=3代入计算即可

y=-2x+5(x-y)²=1所以(3x-5)²=13x-5=±1x=4/3,x=2注意,不是x=-2所以x=4/3,y=7/3x=2,y=1

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

因为,x-y=3xy所以：-3x+6xy+3y/[(7x-5y)-9xy-(3x-y)]=[-3(x-y)+6xy]/[(7x-5y)-9xy-(3x-y)]=[-3*3xy+6xy]/[7x-5y-

∵x-y=4xy∴原式=[2(x-y)+3xy]/[-(x-y)-2xy]=(8xy+3xy)/(-4xy-2xy)=11xy/(-6xy)=-11/6