Question

The sum of first ‘n’ terms of an A.P, whose first term is ‘a’ and last term is ‘l’



A) Sn =
[a+(n+1)d]

B) Sn =
[a - l]

C) Sn =
[2a+(n+1)d]

D) Sn =
[a + l]​

Answer 1

Answer:

Sn = a + (a + d)+(a + 2d) + ... + (ℓ − 2d)+(ℓ − d) + ℓ. 2 n(a + ℓ) . We have found the sum of an arithmetic progression in terms of its first and last terms, a and ℓ, and the number of terms n.

Answer 2

Answer:

SN=N/2(A+L)

THID THE FORMULA OF SUM WHEN ONLY L AND A IS GIVEN OTHER NWISE FORMULA IS SN=N/2(2A+(N-1)D)