Question

A high school auditorium has 18 seats in the first row and 26 seats in the fifth row. What is theexplicit formula for this sequence? How many seats are on the 12 row?

Answer 1

We have the following:

We can see that the increase is constant, in each row it increases by 2, therefore the sequence would be as follows:

$A(n)=18+2\cdot(n-1)$

On the 12 row:

$\begin{gathered} A(12)=18+2\cdot(12-1) \\ A(12)=18+22 \\ A(12)=40 \end{gathered}$

That is, in row 12 there are a total of 40 seats