Question

If the first, second and last term of an A.P. are a, b and 2a respectively. Then its sum is​

Answer 1

Answer:

Step-by-step explanation:

First term = a

Second term = b

Common difference = b-a

Sum of n terms of AP = (first term + last term)(n/2)

nth term = first term + (n-1)(common difference)

2a = a + (n-1)(b-a)

2a = a + nb - na -b +a

2a = 2a +n(b-a) -b

n(b-a) = b

n = (b-a)/b

Sum of AP = (a+2a)((b-a)/2b)

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

= (3ab-3a²)/(2b)