Question

if seventh time the seventh terms of an Ap is equal to the eleventh times it's eleventh term then find its eighteenth term

Answer 1

Answer:

Step-by-step explanation:

let a = first term and d=common difference.

According to question,

7a7 = 11 a11

=>7(a+6d) = 11(a+10d)

=> 7a-11a = 110d-42d

=> -4a = 68d

=>a = -17d  ......(1)

Now , a18 = a +17d  

but a = -17 d  ..by (1)

so put this value , we get,

a18=-17d +17d =0  

Hence proved.

Answer 2

The correct answer is 0.
Hope it helps