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# core 2 help sequences and series watch

1. a series has seventh term 36 and tenth term 30.
find the sum of of the first five terms and the nth term

xxxxx
2. god only knows.
3. u7 = 36
=> a + 6d = 36 ....(1)

u10 = 30
=> a + 9d = 30......(2)

(2) - (1)
=> 3d = -6
=> d = -2

Using (2): a + 9(-2) = 30
=> a=48

Then use sum formula for an arithmetic sequence.
4. (Original post by e-unit)

Then use sum formula for an arithmetic sequence.
Assuming it is an arithmetic series.
5. (Original post by Malik)
Assuming it is an arithmetic series.
Indeed.

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