3x加2y等于5用代数法解二元一次方程组
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1、=3(x+2)-x=3x+6-x=2x+6把x=-3/2代入得=-3+6=32、2x+y=5x-3y=5(2)*22x-6y=10(3)(1)-(3)7y=-5y=-5/7代入(2)得:x=5+1
2x+3y=k-3(1)3x-2y=8k-11(2)3x+2y-5=0(3)由(3)得2y=5-3xy=2分之(5-3x)将y=2分之(5-3x)代入(1)得2x+3×2分之(5-3x)=k-34x+
(1)y=3-1.5x;(2)x=2,y=0x=0,y=3x=1,y=1.5
x=-20/7y=-16/21再问:3x-4等于5,2x加3y等于负8第一题第二题3x加2x=5x加2,2(3x加2y)等于2x加8再答:加题就要加分数,我很忙的,不然太吃亏了再问:你看错了把,这是2
5x-11y=-1式子1-2+10y=16式子2式子1×2+式子2×52(5x-11y)+5(-2x+10y)=-2+8028y=78y=39/14代入式子2-2x+195/7=162x=83/7x=
由②得x=-3+1.5y③把③代入①得y=6把y=6代入③得x=6∴方程组的解为{x=6{y=6
3x+2y=82x-y=34x-2y=67x=14x=2y=1
2x-5y+3=0---(1)ax-y=7--------(2)由(2)得y=ax-7,代入(1)得:2x-5ax+35+3=0,x=-38/(2-5a)将x=-38/(2-5a)代入y=ax-7可得
x=2-6y把此式带入8X+9Y=3则原式8*(2-6y)+9y=316-48y+9y=3-39y=-13y=3把y=3带入x=2-6y解得x=-16
整理8(x-y)=3(x+y)-128x-8y=3x+3y-125x-11y=-12(1)6x+6y=8x-4y+162x-10y=-16x-5y=-8(2)(1)-(2)×5-11y+25y=-12
x+3y=-1(1)3x-2y=8(2)由(1)*3得3x+9y=-3(3)由(3)-(2)得11y=-11,即y=-1代入(1)得x=2即方程组解为x=2,y=-1
x/5-9y=y/3+228y/3=x/5-2y=3x/140-3/14mx>3x+2(m-3)x>2m-3<0x<2/(m-3)=-42/(m-3)=-4m-3=2/-4=-1/2m=3-1/2=5
题目是这样的:(X+Y)/2+(X-Y)/3=6(1)4(X+Y)-3(X-Y)=-20(2)将(1)两边同时乘以6得3X+3Y+2X-2Y=36→5X+Y=36(3)将(2)化解为4X+4Y-3X+
由题意得:x-y=4;3x+y=8解得:x=3,y=-1把x=3,y=-1代入x-3y=k+2解得,k=7
x-2y=0x=2y3y+1=x3y+1=2yy=-1x=-2再问:是方程组x-2y=03y+1=x再答:对啊x=-2y=-1
x+y=8①2.5x-2(x+y)=-1②①代入②,得2.5x-2×8=-12.5x=15x=6所以y=8-x=8-6=2即x=6y=2
2x+5y=8(1)3x+2y=5(2)(1)x2-(2)x5得-11x=-9x=9/11y=14/11