Question

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

Answer 1

Answer:

Bro its 16

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Answer 2

a=9

d=17-9=8

sum=636

solution:-

sn=n/2(2a+(n-1)d)

636=n/2(2(9)+(n-1)8)

636=n/2(18+8n-8)

636=n/2(10+8n)

636×2=n(10+8n)

1272=10n+8n^2

0=8n^2+10n-1272

0=4n^2+5n-636

0=(n-12)(4n+53)

therefore;

n=12

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