不好意思,因为我一个星期没有上课,所以我不会做,

不好意思,因为我一个星期没有上课,所以我不会做,
可能题目会比较多,但也请你帮帮忙,
解方程组
1.2002x + 2003y=6007 x=2 y=1
2003x + 2002y=6008
2.3(x+2) + 4y - 10=0 x=78/19
5(x-2) - 6(y+2)=11 y=- 79/38
3.x + y + z=2 x=3
y + z + w=3 y=1
z + w + x=5 z=-2
w + x + y=8 w=4
4.3x + 2y + 2z=5 x=-1
2x + 3y + 2z=7 y=1
2x + 2y + 3z=9 z=3
5.3x - 2y=3 x=1
7x - 4y=7 y=0
6.x + y - 3z=2a x=-c-b/2-a/2
x - 3y + z=2b y=-b-a/2-c/2
-3x + y + z=2c z=-a-b/2-c/2
7.x :y :z=1 :3 :5 x=2 y=6 z=10
x + y + z=18
8.x/3 = y/2= z/5 x=-3 y=-2 z=-5
2x + 3y - 4z=8
9.4/3x + 3/2y =7 x=1/3 y=1/2
5/x - 6/y =3

1.
2002x + 2003y=6007 ……①
2003x + 2002y=6008 ……②
②-①,得 x - y = 1 ……③
③×2003+①,得4005x = 8010,于是 x=2 ……④
把④代入③,得 y = x-1 = 1
于是x=2,y=1.
2.
3(x+2) + 4y - 10=0 ……① x=78/19
5(x-2) - 6(y+2)=11 ……②
整理方程,得
3x + 4y = 4 ……③
5x - 6y = 33 ……④
③×3+④×2,得
19x = 78 ,于是 x = 78/19 ……⑤
把⑤代入③,有
y = (4-3x)/4 = -79/38
于是,x = 78/19 ,y = -79/38.
3.
x + y + z = 2 … ①
y + z + w = 3 … ②
z + w + x = 5 … ③
w + x + y = 8 … ④
①+②+③+④,得
3(x+y+z+w) = 18
x+y+z+w = 6 …⑤
⑤-①,得 w = 4
⑤-②,得 x = 3
⑤-③,得 y = 1
⑤-④,得 z = -2
4.
3x + 2y + 2z = 5 …①
2x + 3y + 2z = 7 …②
2x + 2y + 3z = 9 …③
①+②+③,得 7(x+y+z) = 21
于是x+y+z = 3
2x + 2y + 2z = 6 …④
①-④,得 x = -1
②-④,得 y = 1
③-④,得 z = 3
5.
3x - 2y = 3 …①
7x - 4y = 7 …②
①×2-②,得 -x = -1,x = 1 …③
代入①,得 y =(3x-3)/2 = 0
于是 x=1,y=0
6.
x + y - 3z = 2a …①
x - 3y + z = 2b …②
-3x + y + z = 2c …③
①+②+③,得
-x-y-z = 2(a+b+c)
x + y + z = -2a -2b -2c …④
④-①得,4z = -4a -2b -2c
于是z = -a-b/2-c/2
④-②得,4y = -2a -4b -2c
于是y = -b-a/2-c/2
④-③得,4x = -2a -2b -4c
于是x = -c-b/2-a/2
7.
x :y :z = 1 :3 :5 ...①
x + y + z = 18 ...②
由①,y = 3x,z = 5x
代入②,得 9x = 18,x = 2
于是 y = 3x = 6
z = 5x = 10
8.
x/3 = y/2= z/5 ...①
2x + 3y - 4z=8 ...②
由①,设x/3 = y/2= z/5 = d,则
x = 3d,y = 2d,z = 5d
代入②,有-8d = 8 ,d = -1
于是 x = 3d = -3
y = 2d = -2
z = 5d = -5
9.
4/3x + 3/2y = 7
5/x - 6/y = 3
设1/3x = m 1/2y = n,那么方程组化为
4m + 3n = 7 ...①
15m - 12n = 3 ...②
①×4+②,得31m = 31,m = 1
代入①,得n = (7-4m)/3 = 1
于是 1/3x = 1,1/2y = 1
解得 x = 1/3 ,y = 1/2.