Show that a 1 , a 2 ,…..a n form an AP where is defined as below : a n = 3+4n Also find the sum of the first 15 terms in each case.

Question

Philoid · Accepted Answer

Given a_n = 3+4n

So, a₁ = 3+4(1) = 7

a₂ = 3+4(2) = 11

a₃ = 3+4(3) = 15

as of now a₁, a₂, a₃ have the same common difference (d) = 4

so given one is A.P

The sum of first 15 terms is given by (s_n) = [2a + (n-1) d]

= [ 2×7 +(15-1) 4]

= 525

Show that a1, a2,…..an form an AP where is defined as below :an = 3+4nAlso find the sum of the first 15 terms in each case.