Question

Which of the following equations could be used to solve for the tenth term of the following sequence? 15, 13, 11, 9, ...

Answer 1

This is an arithmetic sequence, where the first term (a) is 15 and the common difference (d) is -2.
The general formula for the nth term of an arithmetic sequence is:
$n_{th\ term} =a+(n-1)d$
Therefore the required equation is:
$10_{th} \ term=15+(10-1)\times-2$