Geometric sequences C2 Watch

christinajane
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#1
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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://0e90d90be05fe2865012661b731d...apter%2007.pdf

Hope you can help me!

Thanks
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Makhib19
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The a can be the same as r, it's just a coincidence
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the bear
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there is no connexion between a and r.

if they are the same it is a coincidence.
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Makhib19
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Remember a is the first number in the sequence whereas r is the common ratio (divide two consecutive terms)
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christinajane
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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
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Makhib19
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But you start of with £1000, which you can simply to a = 1?
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Makhib19
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The 5% only applies after first year i.e. next year would be 1.05 etc
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christinajane
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That simple??
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Makhib19
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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
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christinajane
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Thank you for your help!

I am enjoying it but just have to work extra hard because I dont have a maths brain :-(
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