1.3x+2y+z=13x+y+2z=72x+3y-z=122.x+2y+3z=11x-y+7z=10x+3y+2z=23.若方程组4x+3y=1ax+(a-1)y=3的解,x、y相等,则a的值为_______A.4 B.10 C.11 D.12请说出答案以及解题思路
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![1.3x+2y+z=13x+y+2z=72x+3y-z=122.x+2y+3z=11x-y+7z=10x+3y+2z=23.若方程组4x+3y=1ax+(a-1)y=3的解,x、y相等,则a的值为_______A.4 B.10 C.11 D.12请说出答案以及解题思路](/uploads/image/z/998459-35-9.jpg?t=1.3x%2B2y%2Bz%3D13x%2By%2B2z%3D72x%2B3y-z%3D122.x%2B2y%2B3z%3D11x-y%2B7z%3D10x%2B3y%2B2z%3D23.%E8%8B%A5%E6%96%B9%E7%A8%8B%E7%BB%844x%2B3y%3D1ax%2B%EF%BC%88a-1%EF%BC%89y%3D3%E7%9A%84%E8%A7%A3%2Cx%E3%80%81y%E7%9B%B8%E7%AD%89%2C%E5%88%99a%E7%9A%84%E5%80%BC%E4%B8%BA_______A.4+B.10+C.11+D.12%E8%AF%B7%E8%AF%B4%E5%87%BA%E7%AD%94%E6%A1%88%E4%BB%A5%E5%8F%8A%E8%A7%A3%E9%A2%98%E6%80%9D%E8%B7%AF)
1.3x+2y+z=13x+y+2z=72x+3y-z=122.x+2y+3z=11x-y+7z=10x+3y+2z=23.若方程组4x+3y=1ax+(a-1)y=3的解,x、y相等,则a的值为_______A.4 B.10 C.11 D.12请说出答案以及解题思路
1.3x+2y+z=13
x+y+2z=7
2x+3y-z=12
2.x+2y+3z=11
x-y+7z=10
x+3y+2z=2
3.若方程组4x+3y=1
ax+(a-1)y=3的解,x、y相等,则a的值为_______
A.4 B.10 C.11 D.12
请说出答案以及解题思路
1.3x+2y+z=13x+y+2z=72x+3y-z=122.x+2y+3z=11x-y+7z=10x+3y+2z=23.若方程组4x+3y=1ax+(a-1)y=3的解,x、y相等,则a的值为_______A.4 B.10 C.11 D.12请说出答案以及解题思路
1.3x+2y+z=13 ①
x+y+2z=7 ②
2x+3y-z=12 ③
①+③ 5x+5y=25 ④
①×2 6x+4y+2z=26 ⑤
⑤-② 5x+3y=19 ⑥
④-⑥ 2y=6 y=3 x=2 z=1
2.x+2y+3z=11 ①
x-y+7z=10 ②
x+3y+2z=2 ③
①-② 3y-4z=1 ④
①-③ -y+z=9 ⑤
得 y=-37 z=-28
X=169
3.若方程组4x+3y=1
ax+(a-1)y=3的解,x、y相等,则a的值为_B______
A.4 B.10 C.11 D.12
X=y x=y=1/7
代入下式得a=10
3x+2y+z=13...............1
x+y+2z=7.......................2
2x+3y-z=12..................3
1式+3式得
5x+5y=25
x+y=5............4
将4式代入2式得
5+2z=7
2z=2
z=1..................
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3x+2y+z=13...............1
x+y+2z=7.......................2
2x+3y-z=12..................3
1式+3式得
5x+5y=25
x+y=5............4
将4式代入2式得
5+2z=7
2z=2
z=1..................5
将5式分别代入1式,3式得
x+2y+3=11
x+2y=8.................6
x+3y+2z=2
x+3y=0..............7
7式-6式得
y=-8...............8
将8式代入7式得
x+3*(-8)=0
x=24
所以x=24,y=-8,z=1
x+2y+3z=11........................1
x-y+7z=10...............2
x+3y+2z=2................3
1式-2式得
3y-4z=1..............4
3式-2式得
4y-5z=-8.................5
4式*4-5式*3得
-z=28
z=-28......................6
将6式代入4式得
3y-4*(-28)=1
3y=-111
y=-37...............7
将6式,7式代入1式得
x+2*(-37)+3*(-28)=11
x-74-84=11
x-158=11
x=169
所以x=169,y=-37,z=-28
3.若方程组4x+3y=1
ax+(a-1)y=3的解,x、y相等,则a的值为_______
A.4 B.10 C.11 D.12
C.11
4x+3y=1
x、y相等
4x+3x=1
7x=1
x=1/7
x=y=1/7
ax+(a-1)y=3
a/7+(a-1)/7=3
a+a-1=21
2a=22
a=11
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