(代入消元法)
2(x+y)-3x=4---------(1)
3(x-y)+5y=12--------(2)
數學(代入消元法)
2008-02-24 1:09 am
回答 (2)
2008-02-24 1:45 am
✔ 最佳答案
(1) 2(x+y)-3x=42x+2y-3x=4
2y-4=x
(2) 3(x-y)+5y=12
3x-3y+5y=12
3x+2y=12
3(2y-4)+2y=12
6y-12+2y=12
8y=24
y=3
(1) 2y-4=x
2(3)-4=x
2=x
2008-02-24 1:15 am
2(x+y)-3x=4 ---- 1
3(x-y)+5y=12 ---- 2
從1:
2(x+y)-3x=4
2x+2y-3x=4
2y-x=4
2y=4+x
y=(4+x)/2----(3)
把３代入２
3(x-y)+5y=12
3x-3y+5y=12
3x+2y=12
3x+2[(4-x)/2]=12
3x+4-x=12
2x=8
x=4
把ｘ＝４代入１
2(x+y)-3x=4
2(4+y)-3(4)=4
8+2y-12=4
2y-4=4
2y=8
y=4
3(x-y)+5y=12 ---- 2
從1:
2(x+y)-3x=4
2x+2y-3x=4
2y-x=4
2y=4+x
y=(4+x)/2----(3)
把３代入２
3(x-y)+5y=12
3x-3y+5y=12
3x+2y=12
3x+2[(4-x)/2]=12
3x+4-x=12
2x=8
x=4
把ｘ＝４代入１
2(x+y)-3x=4
2(4+y)-3(4)=4
8+2y-12=4
2y-4=4
2y=8
y=4
收錄日期: 2021-04-20 18:37:04
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20080223000051KK02876