Question 4 (x)
Which of the following are APs? If they form an A.P. find the common difference d and write three more terms.
(x) a, 2a, 3a, 4a …
(x) a,2a,3a,4a……
Here,
a2−a1=2a−a=aa3−a2=3a−2a=aa4−a3=4a−3a=a
⇒an+1−an is same everytime.
Therefore, d=a and the given numbers are in A.P.
Next three terms are:
a5=4a+a=5aa6=5a+a=6aa7=6a+a=7a