Answers (6)

a+ar = 15 From this you can find a. t2 = Infinite sum - Sum of first two. You can try solving after this.

Sir I am getting the answer by applying this. But I can't able to understand this formula i.e. "t2= sum to infinite-sum of first two"

Sum of first two terms is given in question. You need not apply formula again.

OK Sir. I understood.