This is the basic and conceptual question from Chapter name- Arithmetic Progression
Chapter number- 9
Exercise 9.6
In this question we have been given an arithmetic progression. And we have to find its sum upto 22 terms
CBSE DHANPAT RAI publications
Class:- 10th
Solutions of CBSE Mathematics
Question 1( v)
Given A.P. has first term(a) = a + b,
Common difference(d) = (a – b) – (a + b) = -2b
and number of terms(n) = 22
So, Sum of A.P. = S22 = n[2a + (n – 1)d] / 2
= 22[2(a + b) + (22 – 1)(-2b)]/2
= 11{2(a + b) – 22b)
= 11(2a – 40b) = 22a – 440b
Hence, the sum of the first 22 terms of A.P. is 22a – 440b.