F.3 Maths(送分的)

👨🏻‍🏫 學術台數學

知識就是力量

2008-04-19 4:10 am

Find the value of x and y
3x + y = 2.2
7x + y = 3.8

更新1:

solidum點解你要delete答案?

更新2:

It is a easy question.

回答 (5)

自由人

2008-04-19 4:47 am

✔ 最佳答案

3x + y = 2.2－－－(1)
7x + y = 3.8－－－(2)
Form (1), y=2.2-3x－－－(3)
sub (3) into (2)
7x+(2.2-3x)=3.8
4x=1.6
x=0.4
sub x=0.4 into (3)
y=2.2-3(0.4)
y=2.2-1.2
y=1.0

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知識就是力量

2008-04-21 5:39 am

我明你想講咩之後你又delete答案- -
我仲想選你做最佳- -

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LOVE

2008-04-19 4:51 am

3x + y = 2.2 ----------(1)
7x + y = 3.8 -----------(2)

(2) - (1):
7x+y - (3x+y) = 3.8 - 2.2
4x = 1.6
x = 0.4

sub x=0.4 into (1):
3(0.4) + y = 2.2
1.2 + y = 2.2
y = 1

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用戶163754

2008-04-19 4:38 am

呢題一定唔係F.3

呢題係 F.2 first term maths curriculum 第 5 課教

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ζ冰τ ofog 改版專員

2008-04-19 4:19 am

7x + y = 3.8
7x = 3.8 - y
x = (3.8 - y) / 7
把以上代入x1

3 * ( (3.8 - y )/ 7 ) + y = 2.2
3 * ( (3.8 - y) / 7 ) = 2.2 - y
(3.8 - y )/ 7 = (2.2 - y)/ 3
11.4 - 3y = 15.4 - 7y
4y = 4
y = 1 代入 x2

7x + 1 = 3.8
7x = 2.8
x = 0.4

參考: 自己

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