Find the sum of a = (a-b)/(a+b) d = (3a-2b)/(a+b) - (a-b)/(a+b)

Find the sum

Solution :

a = (a-b)/(a+b)

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

  d = [3a - 2b -(a - b)]/(a + b) 

  d = [3a - 2b -a + b]/(a + b) 

  d  = (2a - b) / (a + b)

Sn  = (n/2)[2a + (n - 1)d]