Question

how many terms of the ap 9,17,25 must be taken to give a sum of 636 ?
{NOTE : ^ = square }

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

636×2 =n (18+8n=8 )
636×2 = n (10+8n)
636×2 =10n +8n^
636 = 5n +4n^
4n^ +5n =636
4n^ +5 n -636=0
4n^+53n-48n -636=0
n (4n+53) -12 (4n+53) =0
(4n +53) (n-12) =0

4n +53 = 0
n-12 =0
n= 12+0
n= 12
answer is 12

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Answer 1

Answer:

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