解方程组:3x-7y=3,3x-8y=2
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第一题(x+2)²-(y-3)²=(x+y)(x-y)x-3y=2x=3/2y=-1/6第二题3x+2y=72x+3y=18x=-3y=8第三题x-21/53/2x-9≤-7x不存
(1)+(2)得10x+10y=120x+y=12(3)(1)-(3)×3得4y=27∴y=27/4把y=27/4代入(3)得x=21/4∴方程的解是x=21/4y=27/4
(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
3x+y=k①x+3y=2②②乘以3,得3x+9y=6③③减去①,得8y=6-ky=(6-k)/8将y=(6-k)/8代入②中,得x+3(6-k)/8=2x=2-3(6-k)/8因为x,y
y=3(x-y),x=2(x-y)x=0y=0再问:请问,怎样解=0,要过程,谢谢再答:y=3(x-y)=3x-3y4y=3xy=3x/4x=2(x-y)=2x-2y=2x-3x/2=x/2x-x/2
0.8(x+y)=1(x+y)-13.6———把左边的0.8(x+y)与右边x+y相减13.6=0.2(x+y)68=x+yx=49,y=19再问:49和19哪来的
{5(x+y)+3(x-y)=2{7(x+y)-3(x-y)=-6原方程组化简得﹛4x+y=1(1)2x+5y=-3(2)(1)×5得20x+5y=5(3)(3)-(2)得18x=8x=4/9代入(1
x=y+3(1)(10y+x)+(10x+y)=99整理得:x-y=3(3)x+y=9(4)(4)-(3)得,2y=6∴y=3把y=3代入(1)得,x=3+3∴x=6∴原方程组的解是:x=6y=3
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/3+y/7=7(1)x/2-y/3=-1(2)(1)×7+(2)×37x/3+3x/2=49-323x/6=46x=12y=7(7-x/3)=21
1乘以12的4x+3y=243再乘以3得12x+9y=7242乘以4得12x-16y=-2854-5得12x+9y-12x+16y=72-(-28)9y+16y=10025y=100y=4把y=4代入
8x+3y+2=0①6x+5y+7=0②①×5得40x+15y+10=0②×3得18x+15y+21=0两式相减:22x-11=0解得x=1/2代入①得4+3y+2=0解得y=-2所以方程组的解为x=
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-
{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+
若3x>y则方程互相矛盾,所以3x<>y,解得x=9/10,y=21/5
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
3x-7y=3①3x-8y=2②①-②-7y+8y=3-2y=1∴x=(3+7)÷3=10/3即:方程组的解为x=10/3;y=1再问:①-②的那个过程再答:①-②:(3x-7y)-(3x-8y)=3
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
3x-7y=3①3x-8y=2②①-②y=1∴x=(3+7)÷3=10/3即:方程组的解为x=10/3;y=1
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/