Question

The sixth term is 22 and the common difference is 6. What is the fifteenth term?

Answer 1

`T_n = a_1+ d(n-1)`

Given that d = 6 and 6th term is 22,

`22 = a_1+ 6(6-1)`

`22 = a_1+ 30`

`a_1 = 22- 30`

`a_1 = -8`

So the general equation is

`T_n = -8 + 6(n-1)`

`T_n = -8 + 6n-6`

`T_n =6n-14`

When n = 15,

`T_(15) = 6(15)-14`

`T_(15) = 136`

Answer: 136