Question

Sn = n(n+1)/2, find t, and check it is A.P. or not.​

Answer 1

Answer:

Sn = (n)(n + 1)/2

» S (n + 1) = (n + 1) (n + 2)/2

Now, t (n + 1) = (n + 1)/2 [ n + 2 - n]

» t (n + 1) = n + 1

» tn = n

d = t (n + 1) - tn

» d = n + 1 - n = 1

» d = 1 = constant

Therefore, it forms an A.P.