中2數學subject

👨🏻‍🏫 學術台數學

[匿名]

2013-07-31 7:11 am

S= n×(n+1) 咁個subject係n 要點做?
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2

更新1:

S= n×(n+1) -------------- 2 姐係2份之n×(n+1)

更新2:

sq. root 係點解?

回答 (1)

Tony

2013-07-31 8:01 am

✔ 最佳答案

S = n(n+1)/2
2S = n^2 + n
n^2 + n - 2S = 0
n = { -1 ± sq. root[ 1^2 - 4(1)(-2S) ] } / 2
n = [ -1 ± sq. root(1+8S) ] / 2

2013-08-11 07:02:12 補充：
sq. root 係點解?
sq. root 係平方根

參考: myself

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