Question

the 13th term of the series is is 1+5+9.......​

Answer 1

Answer:

A = 1 , d = 5 - 1 = 4 ,

T13 = a + (n-1)d

= 1 + (13-1)×4

= 1 + 12 × 4

= 1 + 48 = 49.

Hope it helps