Question

If pn= pn-1 +4 and p17=74, then p3=

Answer 1

$p_n=p_{n-1}+4$
$\implies p_{17}=p_{16}+4$
$\implies p_{17}=p_{15}+2\cdot4$
$\implies p_{17}=p_{14}+3\cdot4$
$\implies p_{17}=\cdots=p_3+14\cdot4$

$\implies74=p_3+56\implies p_3=18$