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# C1 arithmetic series

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1. How would you find P?
(Yes I have looked at the mark scheme- I don't really understand it)
2. 2p/(12-p)=(4p-5)/2p. You then cross multiply and solve the quadratic equation 😀
3. (Original post by Questioness)

How would you find P?
(Yes I have looked at the mark scheme- I don't really understand get it)
It's an arithmetic series, so the difference between the second and third term is the same as the difference between the second and first term (i.e: common difference).

What is the difference between the first and second term? (Second - first)

What is the diffence between the second and third term (third - first)

Equate those to get an equation involving p which you can then solve.
4. (Original post by Zacken)
It's an arithmetic series, so the difference between the second and third term is the same as the difference between the second and first term (i.e: common difference).

What is the difference between the first and second term? (Second - first)

What is the diffence between the second and third term (third - first)

Equate those to get an equation involving p which you can then solve.
Okay, thanks for the explanation .
5. (Original post by Questioness)
Okay, thanks for the explanation .
No problem.
6. (Original post by Cardboard5678)
2p/(12-p)=(4p-5)/2p. You then cross multiply and solve the quadratic equation 😀
That's the method for a geometric sequence, not an arithmetic one
7. (Original post by Fangedbeast)
That's the method for a geometric sequence, not an arithmetic one
Oh yeah. Oops just been revising c2. It's subtract rather then divide then 😳

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