Select the correct answer.

Each month, Barry makes three transactions in his checking account:
- He deposits [tex]$\$700$[/tex] from his paycheck.
- He withdraws [tex]$\[tex]$150$[/tex][/tex] to buy gas for his car.
- He withdraws [tex]$\$400$[/tex] for other expenses.

If his account balance is [tex]$\[tex]$1,900$[/tex][/tex] at the end of the 1st month, which recursive equation models Barry's account balance at the end of month [tex]$n$[/tex]?

A. [tex]f(1)=1,900[/tex]
[tex]f(n)=150 \cdot f(n-1)[/tex], for [tex]n \geq 2[/tex]

B. [tex]f(1)=1,900[/tex]
[tex]f(n)=f(n-1)+150[/tex], for [tex]n \geq 2[/tex]

C. [tex]f(1)=1,900[/tex]
[tex]f(n)=f(n-1)-150[/tex], for [tex]n \geq 2[/tex]

D. [tex]
\begin{array}{l}
f(1)=1,900 \\
f(n)=f(n-1)+700, \text { for } n \geq 2
\end{array}
[/tex]



Answer :

Let's analyze the problem step-by-step to determine the correct answer for the recursive equation modeling Barry's account balance.

1. Initial Balance:
- Barry's starting balance at the end of the first month is \[tex]$1,900. - Therefore, at the end of month 1, the account balance \( f(1) \) is \$[/tex]1,900.
- Thus, one component of the recursive equation is [tex]\( f(1) = 1,900 \)[/tex].

2. Monthly Transactions:
- Barry deposits \[tex]$700 from his paycheck. - He withdraws \$[/tex]150 for gas.
- He withdraws \[tex]$400 for other expenses. 3. Net Monthly Change: - To find the net change in the balance each month, calculate the total withdrawals: \[ \text{Total withdrawals} = \text{withdrawal for gas} + \text{withdrawal for other expenses} = 150 + 400 = 550 \text{ dollars} \] - The net change per month would be: \[ \text{Net change} = \text{deposit} - \text{total withdrawals} = 700 - 550 = 150 \text{ dollars} \] - This means that each month, Barry's balance increases by \$[/tex]150.

4. Recursive Equation:
- The recursive equation for the balance at the end of month [tex]\( n \)[/tex] can be expressed as:
[tex]\[ f(n) = f(n-1) + 150, \quad \text{for } n \geq 2 \][/tex]
- This satisfies the condition that each month the account balance increases by \$150 due to the net change after deposits and withdrawals.

Given the choices, the correct answer is:

D.
[tex]\[ \begin{array}{l} f(1) = 1,900 \\ f(n) = f(n-1) + 150, \text{ for } n \geq 2 \end{array} \][/tex]

This matches the correct net monthly change and indicates the growth in the account balance accurately.