sigma equation S4 M2

👨🏻‍🏫 學術台數學

alpha

2011-10-31 5:36 am

Evaluate the following sums

a)
4
Σ 1
i=1

b) 4
Σ i^2
i=1

hence evaluate

4
Σ [(i+1)(i-1)]
i=1

can anyone explain this briefly to me please.. thx a lot

更新1:

why (a) is 1+1+1+1 ?? THANKS

回答 (2)

myisland8132

2011-10-31 5:41 am

✔ 最佳答案

(a) The value is equal to 1 + 1 + 1 + 1 = 4

(b) The value is equal to 1^2 + 2^2 + 3^2 + 4^2 = 30

(c) The value is equal to 2 * 0 + 3 * 1 + 4 * 2 + 5 * 3 = 26

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匿名

2011-11-01 2:14 am

Q:why (a) is 1+1+1+1 ??
A:
Since the i is with respective to the i in the term 1,
as 1 does not have i,
we concludes that each term in the summation will not be affected.
Therefore, it equals 1+1+1+1 = 4

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