Question

Find the 5and term of the arithmetic sequence 5, 9, 13,

Answer 1

Notice that:

$\begin{gathered} 9-5=4, \\ 13-9=4. \end{gathered}$

Since the sequence is arithmetic then, the nth term has the following form:

$a_n=5+4\cdot(n-1)\text{.}$

Therefore:

$a_{52}=5+4(51)=5+204=209.$

Answer: 209.