How many terms of the AP: 9, 17, 25, ... must be taken to give a sum o

1.	How many terms of the AP: 9, 17, 25, ... must be taken to give a sum of 636?
Answer» 12 Term be 12 , -53/4 .. 12 S=n/2(2a+(n-1) d) 636n=n/2(2*9+(n-1) 8) 318n=n(18+8n-8) 318n=n(10+8n) 318n=10n+8n^2318n-10n=8n^2

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