Geometric sequences C2

Hello,

I just need something clearing up for me regarding sequences.

In some questions - in the edexcel mixed exercise in book c2 chapter 7 from questions 12 -16. The value of a = 1 - when in other seemingly similar questions the value of a is also the same as the value of r....

I cant quite work out why its different when the questions kinda follow the same pattern...

This is the link for the solutions from chapter 7 and specifically the last few questions of the mixed exercise at the end so you can see what I am trying to explain...

https://0e90d90be05fe2865012661b731d0adbe5865fd8.googledrive.com/host/0B1ZiqBksUHNYT1JhVExXbEs2dk0/C2%20Chapter%2007.pdf

Hope you can help me!

Thanks

Reply 1

Makhib19

The a can be the same as r, it's just a coincidence

Reply 2

the bear

there is no connexion between a and r.

if they are the same it is a coincidence.

Reply 3

Makhib19

Remember a is the first number in the sequence whereas r is the common ratio (divide two consecutive terms)

Reply 4

christinajane

I know but in question 15 for example I set a = to 1.05 the same as r because thats what I got when I wrote the sequence out and it seemed to follow the other questions I did.

But the answer was wrong and that was coz a = 1 in this case - I jsut didnt understand why and there are a few questions like that where I am not sure why a =1

Reply 5

Makhib19

But you start of with £1000, which you can simply to a = 1?

Reply 6

Makhib19

The 5% only applies after first year i.e. next year would be 1.05 etc

That simple??

Yes, you have over complicated it. But good on you that you are thinking deeply. I o Advanced Higher Maths in Scotland, similar to A Level in England and I greatly enjoy it. Best wishes :smile: