College

Consider the given recursive function of an arithmetic sequence:

[tex]
\[
\begin{array}{l}
f(1)=4 \\
f(n)=f(n-1)+7, \text{ for } n=2,3,4, \ldots
\end{array}
\]
[/tex]

What is the [tex]8^{\text{th}}[/tex] term of the sequence?

A. 67
B. 60
C. 46
D. 53

Answer :

To find the [tex]\(8^{\text{th}}\)[/tex] term of the sequence, we need to understand how arithmetic sequences work. An arithmetic sequence has a pattern where each term is a fixed amount more than the previous term. This fixed amount is called the common difference.

For the given sequence:

1. The first term is [tex]\(f(1) = 4\)[/tex].
2. The common difference is [tex]\(7\)[/tex].

To find any term in an arithmetic sequence, you can use the formula for the [tex]\(n^{\text{th}}\)[/tex] term:

[tex]\[
f(n) = f(1) + (n - 1) \times \text{common difference}
\][/tex]

In this problem, we need to find the [tex]\(8^{\text{th}}\)[/tex] term ([tex]\(f(8)\)[/tex]). Let's plug the values into the formula:

- The first term, [tex]\(f(1)\)[/tex], is 4.
- The common difference is 7.
- We want the [tex]\(8^{\text{th}}\)[/tex] term, so [tex]\(n = 8\)[/tex].

Use the formula:

[tex]\[
f(8) = 4 + (8 - 1) \times 7
\][/tex]

Calculating this step-by-step:

- Calculate [tex]\(8 - 1\)[/tex], which is 7.
- Multiply 7 by the common difference, which is 7, so [tex]\(7 \times 7 = 49\)[/tex].
- Add this result to the first term: [tex]\(4 + 49 = 53\)[/tex].

Therefore, the [tex]\(8^{\text{th}}\)[/tex] term of the sequence is [tex]\(53\)[/tex].

The correct option is D. 53.

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