3x-2y=1 x-y=3方程组怎么解

两式相加3（x+y）-3(x-y)=46y=4xy=2/32x+2y-x+y=3x+3y=3x=3-3y=3-2=1

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,

（用换元法）设A=x+y,B=x-y原方程组可化为2A-3B=1,6A+7B=51解得A=5,B=3即x+y=5,x-y=3解得x=4,y=1

将①带入②式得2(y-2/y-1)=(3/y+2)+12y-4/y-2=(3/y+2)+12y²-5y-7=0(2y-7)(y+1）=0得y1=2/7,y2=－1把y1=2/7,y2=－1代

.死算呗xy-2x+3y-6=xy+10x-3y-30,2x-y=4xy+3x+y+3=xy+12x-2y-24,3x-y=92式减1式,x=5,y=6

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.

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

2x+y+1/y=8这个式子重新写下,写成这样就好看了x+1/y+x+y-3=5然后再假设根号(x+1/y)=m根号(x+y-3)=n那么m+n=3m*m+n*n=5解方程组有两组答案第一组m=1n=

{(x-2)(y+3)=(x+1)(y-1){(x+1)(y+1)=(x-1)(y+5){xy+3x-2y-6=xy-x+y-1{xy+x+y+1=xy+5x-y-5{4x-3y=5(1){4x-2y

因为2(x+y)-3(x-y)=1所以2x+2y-3x+3y=1-x+5y=1x=5y-1因为6(x+y)+7(x-y)=51所以6x+6y+7x-7y=5113x-y=51将x=5y-1代入13x-

先把第二个式子两边同乘以6,则第二个式子就变为3（x+y）+(x-y）=6{1}第二个式子减第一个式子得（x-y）=2{2}x-y=2/5将上式带入{1}中得x+y=28/15{3}由{2}{3}得x

｛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+

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

解将x+y=3代入1/2(x+y)-3y=5∴1/2×3-3y=5∴3y=3/2-5∴3y=-7/2∴y=-7/6∴x=25/6

{2x+y=6①{x-3y=1②①减②得x+4y=57y(x-3y)²-(3y-x)³=7y(x-3y)²+(x-3y)³=7y(x-3y)²+(x-

7Y(X-3Y)^2-(3Y-X)^3=7Y(X-3Y)^2+(X-3Y)^3=(X-3Y)^2(7Y+X-3y)=(X-3Y)^2(X+4Y)因为X-3Y=1所以上式=(X-3Y)^2(X+4Y+X

设1/x+y=t1/x-y=v则3t+2v=17/52t-5v=16t+4v=34/56t-15v=319v=19/5v=1/5t=11/x+y=11/x-y=1/5x+y=1x-y=5x=3y=-2

可能是0＜X0=X0≤X≤1X＞1当0＜X时,｜X+Y｜=1原式=Y-X=1Y=1+X｜X｜+2｜Y｜=3变2（1+X）-X=3X=1所以Y=0当0=X时Y无解,不成立.当0≤X≤1时X+Y=1X+2

(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)