A-Level Maths: D5-07 Geometric Sequences: Examples of Finding the Sum of Geometric Series

[jackkselby]

sorting me out for my mocks, best maths channel

[lukeollerhead]

The sigma notation has a slightly different convention in the Edexcel textbook. It's always n=0 on the bottom and n-1 on the top. Have you seen this before? So for the first 5 terms of a geometric series, you would get n=0 on the bottom and 4 on the top if that makes sense...

[Doodo]

For number 6, why is n=3 I don’t understand why you have to add a 1 to 8-6

[Masowe.]

7:07 where did the 16go?
i am really confused

[olivergilkes]

should you leave your answers as decimals or fractions?

[samv]

For question 2, can you use natural logs as well??

[scottwall]

Q2. Where does the 2187/128 come from? 136.6875/8 = 17.08

[jackhatton]

Hi Jack,

I am following an example on the Edexcel Pure Maths Year 2 book (3.4 - Example 13)

I am struggling to follow one particular part of the example

Line 1: 1024(-1/2)^n-1 = 1
Line 2: (-2)^n-1 = 1024

I can't work out how to get from Line 1 to Line 2!

Any help appreciated.

[tni]

what happens when the common ratio is negative wouldn't it give you a error

[ibrahimmiah]

Do you get given these formulas in the exam?