Question

how many terms of the Ap : 9,17 ,25,... must be taken to give a sum of 636?​

Answer 1

sn =636

636=n/2 (2×9+(n-1)8)

1272=n(18+8n-8)

1272=18n+8n²-8n

8n²+10n-1272

now by middle term you can solve

Answer 2

Answer:

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