Question

Find S₂ for the A.P. 3,5,7,9,......

Answer 1

A.P. 3,5,7,9

Here, a = 3

d = t₂ - t₁ = 5 - 3

d = 2

S_n = `"n"/2[2"a" + ("n"-1)"d"]`

`"S"_2 = 2/2[2(3) + (2-1)2]`

= [6 + 1(2)]

= 6 + 2

= 8