Question

The first, second and last terms of an ap are a, b and 2a, respectively. Then, its sum is

Answer 1

Answer:

3ab/(2(b-a))

Step-by-step explanation:

The first, second and last terms of an ap are a, b and 2a, respectively

First Term  =  a

Second Term = b

Last Term = 2a  =a + (n-1)d

2a = a  + (n-1)(b-a)

a = n(b-a) - b + a

=> n(b-a) = b

=> n = b/(b-a)

Sum of N terms

= (n/2)(a + 2a)

= (3a/2)n

= (3a/2)(b/(b-a))

= 3ab/(2(b-a))