Question

12. I k-1, k + 3 and Sk-1 are three consecutive terms of a AP, find the value of k.​

Answer 1

Since these terms are consecutive terms of an A.P., the middle term must be the average of the other two.

⇒(k−3)+(4k+3)=2(2k+1)

⇒5k=4k+2

⇒k=2

Thus, the required value of k is 2.