Question

A term in an arithmetic sequence and the common difference. Given `a_15=272` and d=20, how do you find the first three terms?

Answer 1

`-8,12,32`

Explanation:

For the standard arithmetic sequence, the nth term is.

`color(red)(bar(ul(|color(white)(2/2)color(black)(a_n=a_1+(n-1)d)color(white)(2/2)|)))`
where `a_1" is first term"`

here `a_15=272" and " d=20`

and we want to find `a_1,a_2" and " a_3`

`rArr272=a_1+(14xx20)`

`rArra_1=272-280=-8`

`rArra_2=-8+d=-8+20=12`

`rArra_3=12+20=32`