Chapter 11: Problem 43
Find the indicated term of each sequence. The fifteenth term of the arithmetic sequence \(\frac{3}{2}, 2, \frac{5}{2}, \ldots\)
Short Answer
Expert verified
The 15th term is \(\frac{17}{2}\) or \(8\frac{1}{2}\).
Step by step solution
01
Identify the First Term and the Common Difference
The first term of the sequence is given as \(a_1 = \frac{3}{2}\). The second term is \(2\), so the common difference (\(d\)) can be calculated as follows: \(d = 2 - \frac{3}{2} = \frac{1}{2}\). Thus, the common difference is \(\frac{1}{2}\).
02
Write the General Formula for the n-th Term
The general formula for the n-th term of an arithmetic sequence is given by \(a_n = a_1 + (n-1) \times d\). Here, \(a_1 = \frac{3}{2}\) and \(d = \frac{1}{2}\).
03
Substitute the Values to Find the 15th Term
Substitute \(n = 15\), \(a_1 = \frac{3}{2}\), and \(d = \frac{1}{2}\) into the formula: \[a_{15} = \frac{3}{2} + (15-1) \times \frac{1}{2}\]
04
Simplify the Expression
First, calculate the multiplication: \((15-1) \times \frac{1}{2} = 14 \times \frac{1}{2} = 7\). Then add to the first term: \[a_{15} = \frac{3}{2} + 7 = \frac{3}{2} + \frac{14}{2} = \frac{17}{2}\]
05
Convert to Mixed Number (Optional)
The fraction \(\frac{17}{2}\) can be expressed as a mixed number: \(\frac{17}{2} = 8\frac{1}{2}\). Thus, the 15th term is \(8\frac{1}{2}\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Common Difference
Every arithmetic sequence follows a pattern where the difference between consecutive terms remains constant. This fixed difference is known as the "common difference." For instance, take the sequence given in the exercise:
- First term: \( \frac{3}{2} \)
- Second term: 2
N-th Term Formula
To find any term in an arithmetic sequence, use the n-th term formula, a simple mathematical expression:\[ a_n = a_1 + (n-1) \times d \]In this formula:
- \(a_n\) is the n-th term in the sequence.
- \(a_1\) is the first term.
- \(n\) denotes the term position you want to find.
- \(d\) is the common difference.
Sequence Terms
In an arithmetic sequence, each term follows a particular order dictated by its position and the common difference. If you're given a sequence, you can predict future terms by using:
- The first term (starting point), which is \(\frac{3}{2}\) in our example.
- The common difference, which is \(\frac{1}{2}\).
- Second term: \( \frac{3}{2} + \frac{1}{2} = 2 \)
- Third term: \( 2 + \frac{1}{2} = \frac{5}{2} \)
- Fourth term: \( \frac{5}{2} + \frac{1}{2} = 3 \)
Mixed Numbers
Fractions can sometimes be converted into mixed numbers for easier understanding or simplification. A mixed number consists of a whole number and a proper fraction. For example, in the solution:
- The 15th term is \( \frac{17}{2} \).
- The mixed number form is \( 8\frac{1}{2} \).
- 17 divided by 2 is 8 with a remainder of 1.
- This makes the expression \( 8\frac{1}{2} \).