Question

o numero de termo da PA (6,9...,84) é?

Answer 1

$PA (6,9...,84) \\\\\\ a_1=6\\ a_n=84\\r=9-6=3\\ n=?\\\\\\ a_n=a_1+(n-1)*r\\\\\\ 84=6+(n-1)*3\to \\ \\84=6+3n-3\to \\\\ 84-6+3=3n\to \\\\81=3n\to \\\\ \frac{81}{3} =n\\\\ n=27$