# Thread: Sequences and Series - summation notation

1. ## Sequences and Series - summation notation

1. Determine the approximate value of

2. Evaluate

3. Find the value of the 8th term of the series 9(4)j - 6.

2. Originally Posted by danield3
1. Determine the approximate value of

2. Evaluate

3. Find the value of the 8th term of the series 9(4)j - 6.
Do you understand what $\displaystyle \sum$ means? What have you tried and where are you stuck?

3. Originally Posted by mr fantastic
Do you understand what $\displaystyle \sum$ means? What have you tried and where are you stuck?
I do not know how to do it. Can you help me.

4. Originally Posted by danield3
I do not know how to do it. Can you help me.
It would help if you had answered the two questions I asked you (or at leats the first question).

Q1 By definition: $\displaystyle \sum_2^8 3^{k-1} = 3^1 + 3^2 + 3^3 + 3^4 + 3^5 + 3^6 + 3^7 = .....$ and you can go to a calculator and evaluate. Alternatively, if you've been taught about geometric series, you can use the usual formula to evaluate it (a = 3, r = 3, n = 7).

The other two are left for you to attempt. Please show what you have done. Say where you are stuck.