How many terms of the A.P 9,17,25,......must be tak3n to give a sum of

1.	How many terms of the A.P 9,17,25,......must be tak3n to give a sum of 636
Answer» a=9 d=4 Sn=636 n=?Sn=n/2(2a+(n-1)d)636=n/2(18+(n-1)4)6362=n(18+4n-4)1272=n(14+4n)1272=14n+4nn4n square+14n-1272=0Now solve this by splitting the middle term

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