Given an arithmetic sequence with $d=-7$ and $a_7=4$ , what is $a_22$ ?

Question

1762 views around the world

You can reuse this answer
Creative Commons License

Answer 1 · 2017-01-13T06:08:46

$a_22=-101$

$n^(th)$ term of an arithmetic sequence, whose first term is $a_1$ and common difference is $d$ is $a_n=a_1+(n-1)d$ .

As $a_7=a_1+(7-1)d=4$ , we have

$a_1+6xx(-7)=4$

or $a_1=4+42=46$

and hence $a_22=46+(22-1)*(-7)$

$=46-21xx7$

$=46-147$

$=-101$

Given an arithmetic sequence with d=-7d=-7 and a_7=4a_7=4, what is a_22a_22?