Mathe~~數學

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要求： A + B = 100

(a) A : B = 1 : 3
可以令 A = k, B = 3k, k 為非零常數
A + B = 100
k + 3k = 100
4k = 100
k = 25
A = k = 25

(b) A : B = 2 : 3
可以令 A = 2k, B = 3k, k 為非零常數
A + B = 100
2k + 3k = 100
5k = 100
k = 20
A = 2k = 40

(a) A:B = 1 : 3
假設 A = n, B = 3 n
A + B = 100
n + 3 n = 100
4 n = 100
n = 25
A = 25

(b) A : B = 2 : 3
假設 A = 2 n, B = 3 n
A + B = 100
2 n + 3 n = 100
5 n = 100
n = 20
2 n = 40
A = 40

2 4 9 17 28 42 的通項是什麼?
2 4 9 17 28 42 general term?

A + B = 100
　　
(a) A:B = 1 : 3
假設 A = n, B = 3 n
A + B = 100
n + 3 n = 100
4 n = 100
n = 25
A = 25

(b) A : B = 2 : 3
假設 A = 2 n, B = 3 n
A + B = 100
2 n + 3 n = 100
5 n = 100
n = 20
2 n = 40
A = 40

希望幫到你！

A和B的和是100
即是A + B = 100
　　
(a) A:B = 1 : 3
假設 A = n, B = 3 n
A + B = 100
n + 3 n = 100
4 n = 100
n = 25
A = 25

(b) A : B = 2 : 3
假設 A = 2 n, B = 3 n
A + B = 100
2 n + 3 n = 100
5 n = 100
n = 20
2 n = 40
A = 40

(a) A:B = 1 : 3

A/B = 1/3

3A = B

A+B = 100

咁 ......

(b)

B/A = 3/2

咁 ......