F.2數學聯立方程

From 2,
x=2+3y ---3

Sub 3 into 1
2(2+3y)+y=9
4+6y+y=9
4+7y=9
7y=5
y=5/7

x=2+3(5/7)
x=14/7+15/7
x=29/7

2007-05-09 23:15:48 補充：
Sorry睇錯左呢個先係From 2,x=1+3y ---3Sub 3 into 12(1+3y)+y=92+6y+y=92+7y=97y=7y=1x=2+3(1)x=2+3=5

{2x+y=9----1
{x-3y=1----2
therfore,x=1+3y----3
Sub 3 to 1
2(1+3y)+y=9
2=6y=y=9
2+7y=9
7y=7
y=1

suby=1to 2
x-3(1)=1
x-3=1
x=4
that's easy^^

{2x+y=9----(1)
{x-3y=1-----(2)

y=9-2x------(3)
(3)>(2)
x-3(9-2x)=1
x-27+6x=1
7x=28
x=4----------(4)
(4)>(3)
y=9-2(4)
y=1

{2x+y=9----1
{x-3y=1----2

2 x2
2x-6y=2----3

1 -3
(2x+y)-(2x-6y)=9-2
2x+y-2x+6y=9-2
7y=7
y=1

Sub y=1 into 2(把 y=1代入1)
x-3y=1
x-3(1)=1
x-3=1
x=4

Therefore(因此), x=4, y=1.


驗算:
1. 2x+y=9
2(4)+1=9
8+1=9
9=9
2. x-3y=1
4-3(1)=1
4-3=1
1=1

Hope I can help you!
希望我能幫到你!

2x+y=9----（1）
x-3y=1----（2）

（1）X3
6x+3y=27----（3）
（3）+（2）
6x+3y+x-3y=1+27
7x=28
x=4

x=4代入（2）
4-3y=1
y=1

將2,
x=1+3y------3
將3代入1,
2(1+3y)+y=9
2+7y=9
y=1
將(y=1)代入1,
2x+1=9
2x=8
x4
所以,,,x=4,y=1

rearrange 2

x-3y = 1
x = 1+3y --- 3

put 3 into 1

2x + y = 9
2(1+3y) + y = 9
2 + 6y + y=9
7y = 9-2
7y = 7
y = 1

(1) x 3, 6x + 3y = 27 ---- (3)
(2) + (3), 7x = 28
x = 4,
用返 (1), y = 1

2007-05-09 23:18:40 補充：
上面果兄台 waves1205 好似搞錯D野,由 (2) 式得 x = 1 + 3y眼大睇過龍

2007-05-09 23:21:15 補充：
錯完又錯,條友好唔掂,x = 1 + (3)(1)x = 4唔夠精神訓訓先