Question

for what value of k will k+9 , 2k -1 and 2k +7 are the consecutive terms of an AP ????

Answer 1

In A.P difference of consecutive terms is same
  (2k-1) - (k+9) = (2k+7) - (2k-1)
 k = 18

Answer 2

Hlw friend!
In ap common difference is equal btw two terms ok?
So we can write it as
2k-1-k-9=2k+7-2k+1
K=18
Hope it helped u!
For any explanation just text me.