Question

An AP has four terms. If its first and last terms are 1 and 5 respectively, then its sum is​

Answer 1

Answer:

answer for the given problem is given

Answer 2

Step-by-step explanation:

a = 1 , a4 = 5 , n= 4

S4 = n/2 [ a + a4 ]

S4 = 4/2 [ 1 + 5 ]

S4 = 2 [ 6 ]

S4 = 12