4X-3Y-3a=0 x-3y-a=0求xy 2ya x平方 y-a的平方的值

3(x+y)+3(y-x)=1(1)3(x+y)+4(y-x)=-1(2)(2)-(1)得y-x=-2(3)代入（1）3（x+y)-6=1x+y=7/3=>x=7/3－y又由（3）得x=y+2y+2=

由(1)得3x+3y+2x-2y=365x+y=36(3)由(2)得4x+4y-3x+3y=-20x+7y=-20(4)(3)×7-(4)得34x=272∴x=8把x=8代入(3)得y=-4∴x=8y

{(x+y)/2+(x-y)/3=63(x+y)+2(x-y)=36(1)4(x+y)-3(x-y)=-20(2)由（1）*3+(2)*2得9(x+y)+6(x-y)+8(x+y)-6(x-y)=36

(2x+y)(2x-3y)+x(2y+y)=(2y+y)(2x-3y+x)=(2y+y)(3x-3y)=3(2y+y)(x-y)2a(x-y)-4b(x-y)=2(x-y)(a-2b)

化简得：-x+7y=11①7x+3y=27②①式×7得：-7x+49y=77③②+③得：52y=104∴y=2代入①得：x=3∴x=3,y=2再问：亲，是代入法哦！再答：代入法①式得3x+3y-4x+

平面区域的三个顶点为O（0,0）,A（0,14/3),B（2,2）（y+1)/(x+2)即是区域内一点P(x,y)与点C(-2,-1)连线的斜率.由数形结合可知1/2≤kPC≤17/6.所以(y+1)

c∵x+y≠0∴x≠-y∵3x-6y/x+y=0∴3x-6y=0∴x=2y∴x=2y且x≠-y

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：{

第二个方程是不是写错了2/（x+y）+3/（x-y）=6是这样吗

x-y=a+32x+y=53x=a+8x=(a+8)/3>0a>-8y=-(2a+1)/3-1/2所以a>-1/2

∵(y-3)/(x-1)=2,x≠1,可化为y-2x=1,∵A∩B=空集,∴y-2x=1方程组无解ay+4x=16∴1/a=-2/4≠1/16解得a=-2又x≠1,则y≠3,∴3a+4≠16,a≠4当

3(x+y)-4(x-y)=4(x+y)/2+(x-y)/6=1令a=x+y,b=x-y3a-4b=4(1)a/2+b/6=1则3a+b=6(2)(2)-(1)5b=2b=2/5a=(6-b)/3=2

（5x+3y)(3y-5x)-(4x-y)(4y+x)=(3y)^2-(5x)^2-(4x^2+15xy-4y^2)=9y^2-25x^2-4x^2-15xy+4y^2=13y^2-15xy-29x^

完整设1/(x+y)=a,1/(x-y)=b原方程组可变为4a+6b=39b-a=1a=9b-136b-4+6b=3b=1/6,a=1/2x+y=2x-y=6所以原方程组的解为：x=4,y=-2

|x-3a|+（y+3）=0,所以X=3a,Y=-3把A=2x-3xy+y+x-3y,B=4x-6xy+2y+4x-y代入B-2A=a,得2X+5Y=a代入X=3a,Y=-3,得a=3所以x=9,y=

绝对值项恒非负,两绝对值项之和=0,两绝对值项分别=03x-y=0(1)x+y=0(2)(1)+(2)4x=0x=0,代入(2)y=-x=0(x-y)/(xy)无意义,因此题目错了.

55分钟前四个肯定发生|二级x-y）²-x+yx²+四分之一y²-xya²-6a（b-c）+9（b-c）²2x²-10x-12已知x-5y=

x²+y²-4x+6y+13=0x²-4x+4+y²+6y+9=0(x-2)²+(y+3)²=0x=2,y=-3代入即可得出答案(3x+y)

x-2y=4+a式子12x+3y=4a式子2式子2-式子1×22x+3y-2(x-2y)=4a-2(4+a)7y=2a-8y=(2a-8)/7y-12/11所以-12/11

我把方法告诉你,最后的答案你自己做吧,很容易.(x+y)(x+2y)(x+3y)(x+4y)=-40(x+y)（x+4y）(x+2y)(x+3y）=-40(x^2+5yx+44)(x^2+5yx+66