已知x2 xy-2y²=0,求x y-y x

x^2+y^2+4x-6y+13=(x+2)^2+(y-3)^2=0所以x=-2y=3所以x^y=-8

(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

2x-3y=0(1)3x-y-1=0(2)由（2）得y=3x-1(3)把y=3x-1代入(1)得2x-9x+3=0∴x=3/7把x=3/7代入（3）得y=2/7∴x=3/7y=2/7

75＝(2x+3y)(3x+2y)　　＝6x＾2＋13xy＋6y＾2　　＝6（x＋y）＾2＋xy＞＝24xy＋xy＝25xyxy＜＝3x＋y＞＝2vxy＝2v3最小值2v3再问：6（x＋y）＾2＋xy

2x+yx2-2xy+y2•(x-y)=2x+y(x-y)2•(x-y)（2分）=2x+yx-y；（4分）当x-3y=0时，x=3y；（6分）原式=6y+y3y-y=7y2y=72．（8分）

x²+y²-2x+4y+5=0（x²-2x+1)+(y²+4y+4)=0(x-1)²+(y+2)²=0x-1=0x=1y+2=0y=-2x+

4x-2y=0→y=2x,把所有的y都用2x替代.结果是-1/7

X/X···这是什么意思···再问：x减y分之x等于x分之x减2y再答：两边同乘x（x-2y）再问：再答：题目是什么····就给个图啊···再问：如图，已知EFGH为矩形，AD⊥Bc于D，交HG于K，

2x=2-3yx>0则2x>0所以2-3y>0y

x^2+2x+y^2-6y+10=0（x+1)²+（y-3)²=0∴x=-1,y=3(x+y)²=（-1+3）²=4

即(x-2y)²=0x-2y=0所以x=2y所以原式=(2x²+2xy-xy-y²)/(4x²-4xy+y²)=(2x²+xy-y²

2x+y/x^2-2xy+y^2)*(x-y)=2x+y/(x-y)^2*(x-y)=2x+y/x-yx-3y=0.x=3y将x=3y带入2x+y/x-y=6y+y/3y-y=7/2（二分之七）

如果是(x-y)/x=x/x-2y,则x:y=2:3(x-y)/x=（x-2y+2y）/x-2y1-y/x=1+2y/(x-2y)-y/x=2y/(x-2y)x/y=(x-2y)/-2yx/y=-1/

x²+4x+y²-2y+5=0x²+4x+4+y²-2y+1=0(x+2)²+(y-1)²=0所以x+2=0y-1=0则x=-2y=1所以x

x=3y代入(2x+y)/(x^2-2xy+y^2)*(x-y)=7y/(9y^2-6y^2+y^2)*(2y)=7/2

x-3y=0x=3y原式=(2x+y)(x-y)/(x²-2xy+y²)=(2×3y+y)(3y-y)/[(3y)²-2×3y×y+y²]=7y×2y/(9y&

(x²－4x＋4)＋(4y²＋8y＋4)=0(x－2)²＋4(y＋1)²=0则：x－2=0且y＋1=0得：x=2、y=－1x＋y=1

√x方-y+√2x+y=0x²-y=0,2x+y=02x+x²=0x(x+2)=0x=0或x=-2x=0y=0x+y=0x=-2y=x²=4x+y=-2+4=2

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－

∵x^2-3y^2=2xy∴x^2-2xy-3y^2=0∴（x+y）（x-3y）=0∵x>0,y>0∴x-3y=0∴x=3y∴x+2y/x-y=3y+2y/3y-y=2y+2/3或=2/3(x+1)如