Question

The 3rd term of an arithmetic sequence is 3/2
. The common difference is 1/2
. Complete the statement.(2 points)
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The explicit formula for the sequence is Response area and the recursive formula for the sequence is Response area.

Answers

GPT-4o mini
To determine the explicit and recursive formulas for the arithmetic sequence, we need to work with the given information.

1. The third term of the arithmetic sequence is \( a_3 = \frac{3}{2} \).
2. The common difference \( d = \frac{1}{2} \).

**Explicit Formula:**

The explicit formula for an arithmetic sequence is given by:

\[
a_n = a_1 + (n - 1) \cdot d
\]

We need to find \( a_1 \) (the first term). The third term can be expressed using the explicit formula:

\[
a_3 = a_1 + (3 - 1) \cdot d
\]
\[
\frac{3}{2} = a_1 + 2 \cdot \frac{1}{2}
\]
\[
\frac{3}{2} = a_1 + 1
\]
\[
a_1 = \frac{3}{2} - 1 = \frac{3}{2} - \frac{2}{2} = \frac{1}{2}
\]

So, we can now substitute \( a_1 \) and \( d \) into the explicit formula:

\[
a_n = \frac{1}{2} + (n - 1) \cdot \frac{1}{2}
\]

This simplifies to:

\[
a_n = \frac{1}{2} + \frac{n - 1}{2} = \frac{1 + n - 1}{2} = \frac{n}{2}
\]

Thus, the explicit formula is:

**Explicit Formula: \( a_n = \frac{n}{2} \)**

**Recursive Formula:**

The recursive formula for the arithmetic sequence is given by:

1. The first term: \( a_1 = \frac{1}{2} \)
2. The recursive relation: \( a_n = a_{n-1} + d \)

Substituting the known common difference:

\[
a_n = a_{n-1} + \frac{1}{2}
\]

Thus, the recursive formula is:

**Recursive Formula: \( a_1 = \frac{1}{2}, \quad a_n = a_{n-1} + \frac{1}{2} \text{ for } n > 1 \)**

You can complete the sentence:

1. The explicit formula for the sequence is **\( a_n = \frac{n}{2} \)**.
2. The recursive formula for the sequence is **\( a_1 = \frac{1}{2}, \quad a_n = a_{n-1} + \frac{1}{2} \text{ for } n > 1 \)**.