Without using the general formula for the n^th term, find which term of the AP : 5, 17, 29, 41,...will be 120 more than its 15^th term. Justify your answer.

Asked by Fathima | 31st Mar, 2017, 05:23: PM

Expert Answer:

The common difference, d = 17 - 5 = 12
Since we are not allowed to use the general formula, we add the common difference to each preceding term.
rightwards double arrow 120 over 12 equals 10
So comma space after space the space 15 th space term comma space 10 space more space terms space are space added space to space get space the space term space which space is space 120 space more space than space the space 15 th space term.
Hence comma space the space required space term equals 15 plus 10 equals 25 th space term

Answered by Rebecca Fernandes | 31st Mar, 2017, 09:55: PM