How many terms of the AP 9\' 17\' 25\'•••••••••••••••must be taken to give a sum of 616

How many terms of the AP 9\' 17\' 25\'••••••••••�

1.	How many terms of the AP 9\' 17\' 25\'•••••••••••••••must be taken to give a sum of 616
Answer» Sn=n/2 (2(9)+(n-1)8)616=n/2(18+8n-8)616= n/2( 10+8n)1272= 10n+8n2Whole divided by 24n2+5n-636=0By solving n= 12,-53/4Therefore n=12 153