99我,help

2007-03-05 1:50 am
maths,
{3x+2y=-1
{2x+3y=6

請用代入消元法計算,PLS

回答 (2)

2007-03-05 1:58 am
✔ 最佳答案
3x+2y=-1---(1)
2x+3y=6---(2)
From (1),y=-(3x+1)/2---(3)
Sub (3) into (2):
2x+3[-(3x+1)/2]=6
4x-3(3x+1)=12
4x-9x-3=12
-5x=15
x=-3---(4)
Sub (4) into (3):
y=-(3x+1)/2
=-[3(-3)+1]/2
=8/2
=4
Therefore x=-3,y=4
2007-03-05 3:42 pm
{3x+2y=-1----------(1)
{2x+3y=6-----------(2)
(1)*2 6x+4y=-2-----(3)
(2)*3 6x+9y=18------(4)
(4)-(3) 5y=20
y=4

把y=4代入公式(1):
3x+8=-1
3x=-9
x=-3

2007-03-06 09:21:13 補充:
so x=-3,y=4

2007-03-06 14:02:36 補充:
我用消元法

2007-03-06 17:25:03 補充:
If use 代入法:從(1)=2y=-1-3x y=-(1-3x)/2把(3)代(2):2x+ 3(-1-3x)/2=62x+3/2(-1-3x)=62x-3/2-9/2x-=612x-9-27x=3615x=-45x=-3把x=-3代入:y=[-1-3(-3)]/2 =[-1+9]/2 =4so I think用消元法恰當.


收錄日期: 2021-04-23 00:10:36
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20070304000051KK03777

檢視 Wayback Machine 備份