Question

If the nth term of AP is 3+4n then find sum of the first 15 term of AP

Answer 1

Answer:600

Step-by-step explanation:

an = 3+4n

a1 = 3+4*1 = 7

a15 = 3+4*15 = 63

Sn = n/2 [a + an]

S15 = 15/2 [7 + 63]

      = 15/2 [80]

      =  15 * 40

S15 = 600

Answer 2

Answer:

Apply given formula to get result:

Step-by-step explanation:$S_{n}=a_{n}-a_{n-1}$