How many terms of the A.P.
must be taken so that their sum is 636?
Sn = 
[2a + (n – 1) d]
636 =
[2(9) + (n – 1) 8]
636 = n [9 + 4n -4]
636 = 5n + 4n2
4n2 + 5n – 636 = 0
n = 12 or n = 
(not possible)
5
How many terms of the A.P.must be taken so that their sum is 636?
Sn = [2a + (n – 1) d]
636 = [2(9) + (n – 1) 8]
636 = n [9 + 4n -4]
636 = 5n + 4n2
4n2 + 5n – 636 = 0
n = 12 or n = (not possible)