解方程组x:y=3:4

x-2y=0①x²+3y-3y²=4②由(1)得：x=2y（3）代入(2)得：4y²+3y-3y²=4y²+3y-4=0(y+4)(y-1)=0y1=

3(x+y)-4(x-y)=4,①x+y/2+x-y/6=1,则3(x+y)+(x-y)=6②②-①,得5(x-y)=2,解得x-y=2/5③代入②,得x+y=28/15④③+④,得2x=34/15,

5x+y=369y-x=2即45y-10+y=36y=1x=7

原方程组变形得：①3﹙x＋y﹚－﹙x－y﹚=4②3﹙x＋y﹚＋﹙x－y﹚=6∴①＋②得：③x＋y=10／3②－①得：④x－y=1∴③＋④得：x=13／6③－④得：y=7／6∴x=13／6,y=7／6.

合并方程组：x+y/2=3x-2y;3x-2y=10+6x+y/4;得出：x=5y/4;从而算出：x=-25/12,y=-5/3.手机打很累.

{{x-y)/3-(x+y)/4=2①{(x-y)/6-(x+y)/8=3②②×2得：(x-y)/3-(x+y)/4=6③①与③矛盾∴原方程组无解

(x+y)/2+(x-y)/3=6①5(x+y)-2(x-y)=4②由①得3x+3y+2x-2y=365x+y=36y=36-5x③由②得5x+5y-2x+2y=43x+7y=4④③代入④得3x+25

设a=x+y,b=x-y原方程组为：a/2+b/3=6,即3a+2b=36,即：12a+8b=1444a-5b=12,即：12a-15b=36相减得：23b=108,得：b=108/23,再得：a=1

方程化为－x+7y=1117x+3y=272将1式化为x=7y-113则将3式代入2式可得7（7y-11）+3y=2752y=104y=2x=7×2-11x=3所以解得x＝3y＝2

2(x-y)/3-x+y/4=-1（1）6(x+y)-4(2x-y)=16（2）（1）方程两边同乘以12得8（x-y）-3(x+y)=-12合并同类项得5x-11y+12=0(3)(2)合并同类项得1

化简得:3(x+y)-4(x-y)=43x+3y-4x+4y=4-x+7y=4-x=4-7yx=7y-4(x+y/2)+(x-y/6)=12x+y/3=12(7y-4)+y/3=114y-8+y/3=

先将第一个等式整理得12X+Y=36,第二个等式整理得-X+9Y=2,由第一个等式得Y=36-12X,通过换元法得-X+9(36-12X)=2,解出X=322/109,再把X=322/109代入-X+

令a=1/(x+y),b=1/(x-y)4a+6b=3(1)9b-a=1(2)(1)+(2)×46b+36b=3+442b=7b=1/6a=9b-1=1/2所以x+y=1/a=2x-y=1/b=6相加

{4/x+y+6/x-y=3{9/x-y-1/x+y=1令1/(x+y)=a,1/(x-y)=b则原方程组为{4a+6b=3{-a+9b=1解得{a=1/2{:b=1/6所以{x+y=2{x-y=6解

｛3x-4y(x-y)=3,2x-3y=12x-3y=1,得x-y=(1+y)/23x-4y(x-y)=3,代入x-y=(1+y)/2,得3x-2y(1+y)=33x-2y-2y²=34y+

x+y/3=x-y/4⑴2x+3y=11⑵由⑴得x+7y=0,x=-7y(3)将(3)代入⑵得y=-1所以x=7

1)1/2x-2y=-74,①x-6y=-12②2①-②得2y=136y=68代入①得x=4202)x／5-y／2=2,化简2x-5y=20①2x+3y=4②①-②得-8y=16y=-2代入①得2x=

3(x+y)-4(x-y)=43x+3y-4x+4y=4x-7y=-4(1)x+y/2+x-y/6=13x+3y+x-y=62x+y=3(2)(1)+(2)×715x=17所以x=17/15y=3-2

因为8/(x+y)+18/(x-y)=4/3,两边乘以3得24/(x+y)+54/(x-y)=4两边同时减去24/(x+y)+24/(x-y)=7/3得30/(x-y)=5/3所以x-y=18代入8/

(x+y)/2+(x-y)/6=1x/2+x/6+y/2-y/6=12x/3+y/3=12x+y=3(1)3(x+y)-4(x-y)=43x+3y-4x+4y=4-x+7y=4(2)(1)+2*(2)