CBSE NCERT Solutions Chapter 5 Arithmetic Progressions Exercise 5.2 Question 18
18. The sum of the 4th and 8th terms of an AP is 24 and the sum of 6th and 10th terms is 44. Find the three terms of the AP.
The sum of 4th and 8th terms of an AP is 24 and sum of 6th and 10th terms is 44.
It means and
Using formula , to find nth term of arithmetic progression, we can say that
These are equations in two variables. Lets solve them using method of substitution.
Using equation , we can say that (1)
Putting (1) in equation , we can say that
Putting value of in equation , we get
Therefore, first term
And, Common difference
Therefore, AP is -13, -8, -3, 2, ....
Its first three terms are -13, -8 and -3.