幫我解解e條用消元法做既方程

2007-02-24 3:05 am
2x+7y-14=0
3x+y=2




pls

回答 (2)

2007-02-24 3:12 am
✔ 最佳答案
2x+7y-14=0 -1
3x+y=2   -2

由2,
7(3x+y)=2(7)
21x+7y=14
21x+7y-14=0 -3

1-3,
   2X+7Y-14=0
-)21x+7y-14=0
-------------
       -19X=0
          X=0
代x=0入2,
3(0)+y=2
y=2
參考: meme
2007-02-24 7:46 am
Let :
2x+7y-14=0 .....(1)
3x+y=2 ....(2)

3*(1) - 2*(2)
=> 6x + 21y - 42 =0
- 6x + 2y = 4
_________________
19y -42 = -4
=> y = 2

Substitute y = 2 into (2)
3x + 2 = 2
=> x = 0

Therefore, x = 0 & y = 2 (Answer)


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