代入消元法

👨🏻‍🏫 學術台數學

用戶118574

2007-03-19 5:56 am

代入消元法
用代入消元法解下列聯立方程..
1) y= x- 1 ,,---(1)
4x+7y=4 ,,---(2)

2)x=3y,,---(1)
2y-3x=28,,---(2)

有冇人可以教下我點計????

更新1:

尼多條= ='' 3) Y=4X+7,,---(1) 4X+Y=7,,---(2) 唔該晒''!!

回答 (1)

用戶23317

2007-03-19 6:08 am

✔ 最佳答案

As y = x - 1

Put ( 1 ) into ( 2 ) : 4x + 7( x - 1 ) = 4

4x + 7x - 7 = 4

11x = 11 ==> x = 1

Then, put x = 1 into ( 1 ) : y = 1 - 1 = 0

Similarily, you can do like this for Q2

Put ( 1 ) into ( 2 ) : 2y - 3(3y) = 28

-7 y = 28 ===> y = -4

Put y = -4 into ( 1 ) : x = 3 ( -4 ) = -12

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