解方程组(共两题):①x+y/2+x-y/3=6 ②3x-2y=4
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解方程组(共两题):①x+y/2+x-y/3=6 ②3x-2y=4
(1)
x+y/2+x-y/3=6 ①
3x-2y=4②
(2)
x+y+z=4 ①
3x+y-2z=0 ②
2x+3y+z=7 ③
(1)
x+y/2+x-y/3=6 ①
3x-2y=4②
(2)
x+y+z=4 ①
3x+y-2z=0 ②
2x+3y+z=7 ③
(1)x+y/2+x-y/3=6①
3x-2y=4②
①×6得 3(x+y)+2(x-y)=36
3x+3y+2x-2y=36
5x+y=36
y=36-5x ③
③代入②得 3x-2(36-5x)=4
3x-72+10x=4
3x+10x=4+72
13x=76
x=76/13 ④
④代入③得 y=36-5(76/13)
y=36-380/13
y=88/13
方程组的解是 x=76/13 y=88/13
(2)x+y+z=4 ①
3x+y-2z=0 ②
2x+3y+z=7 ③
①×2得 2x+2y+2z=8 ④
③-①得 x+2y=3 ⑤
②+④得 5x+3y=8 ⑥
⑤移项得 x=3-2y ⑦
⑦代入⑥得 5(3-2y)+3y=8
15-10y+3y=8
-10y+3y=8-15
7y=7
y=1 ⑧
⑧代入⑦得 x=3-2×1
x=1 ⑨
⑧与⑨代入①得 1+1+z=4
z=4-1-1
z=2
方程组的解是 x=1 y=1 z=2
3x-2y=4②
①×6得 3(x+y)+2(x-y)=36
3x+3y+2x-2y=36
5x+y=36
y=36-5x ③
③代入②得 3x-2(36-5x)=4
3x-72+10x=4
3x+10x=4+72
13x=76
x=76/13 ④
④代入③得 y=36-5(76/13)
y=36-380/13
y=88/13
方程组的解是 x=76/13 y=88/13
(2)x+y+z=4 ①
3x+y-2z=0 ②
2x+3y+z=7 ③
①×2得 2x+2y+2z=8 ④
③-①得 x+2y=3 ⑤
②+④得 5x+3y=8 ⑥
⑤移项得 x=3-2y ⑦
⑦代入⑥得 5(3-2y)+3y=8
15-10y+3y=8
-10y+3y=8-15
7y=7
y=1 ⑧
⑧代入⑦得 x=3-2×1
x=1 ⑨
⑧与⑨代入①得 1+1+z=4
z=4-1-1
z=2
方程组的解是 x=1 y=1 z=2
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