{(x-2y-4)--2=0 (2y z)--2=0 |x-4y z|=0

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

x*x+4y*y+2x*x-4y+2=0应该是x*x+4y*y+2x-4y+2=0可变换为（x+1)^2+(2y-1)^2=0x=-1,y=1/2,剩下的自己做一下,关键是上面一步要会

由已知可得（X-3)(X-3)+(Y+2)(y+2）=0,即可得X=3.Y=-2,待到问题中即可得到答案为1

(x+y)(x-y)-(x+y)=0(x+y)(x-y-1)=0若x-y-1=0y=x-1则4x^2-x^2+2x-1+2x-x+1=03x^2-3x=03x(x-1)=0x=0,x=1y=x-1若x

2y错了即(x²-4x+4)+(y²+6y+9)=0(x-2)²+(y+3)²=0所以x-2=0,y+3=0x=2,y=-3

根据（a+b）^2=a^2+2ab+b^2组合为:X^2+2*2*X+2^2+y^2-2*3*y+3^2=0(x+2)^2+(y-3)^2=0两个因式的和为零,那么只有他们分别为零,即：X+2=0y-

3x=4Y.X/Y=4/3,x-y)/y=(X/Y)-1=1/3,（3x+2y)/(2x+3y)=(4Y+2y)/(8/3y+3y)=18/17（因为3x=4Y,2x=8/3y）再问：若3X-4Y=0

x²+y²+13-4x+6y=0(x²-4x+4)+(y²+6y+9)=0(x-2)²+(y+3)²=0平方项恒非负,两非负项之和=0,两非

(x*x+y*y)(x*x+y*y)-4x*x*y*y=(x^4-2x^2y^2+y^4)=(x^2-y^2)^2=0x^2=y^2x/y=±1(x*x+5xy+y*y)/(x*x+2xy+y*y)=

∵x²+y²-4x+2y+5=0x²-4x+4+y²+2y+1=0(x-2)²+(y+1)²=0x-2=0y+1=0∴x=2y=-14x&#

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^2表示平方X^2+4X+4+Y^2-2Y+1=0(X+2)^2+(Y-1)^2=0因为平方大于=0所以X+2=0Y-1=0X=-2Y=1X^2+Y^2=5

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

已知x^2+4y^2-4x+4y+5=0求(（y^4-x^4）/(y-2x)(x+y))*((2x-y)/(xy-y^2))/((x^2+y^2)/y)的值答案：x²+4y²-4x

x平方+8x+16+y平方+6x+9=0(x+4)平方+(y+3)平方=0∴x+4=0y+3=0∴x=-4,y=-3原式=(x+2y)(x-2y)/(x+2y)平方-x/(x+2y)=(x-2y)/(

线性规则,画出可行性区域,得出x=4/5,y=12/5时,z的最大值为48/25

X平方+Y平方-2X+4Y+5=0=>(x-1)^2+(y+2)^2=0=>x=1,y=-2（2x+y）（2x+y)-(2x-y)平方=8xy=-16

(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+2y-1|+y²+4y+4=0∴|x+2y-1|+(y+2)²=0∴x=5,y=-2(2x-y)²-2(2x-y)(x+2y)+(x+2y)²=[(2x

4x^2+y-4x-6y+10=0(2x-1)^2+(y-3)^2=0x=1/2y=3y/x-x/y=6-1/6=35/6