Chapter 4: Problem 7
Find the first five terms and the 50 th term of each infinite sequence defined. $$a_{n}=2 n-3$$
Short Answer
Expert verified
First five terms: -1, 1, 3, 5, 7. 50th term: 97.
Step by step solution
01
Identify the Formula for the Sequence
The given formula for the sequence is \( a_{n} = 2n - 3 \). This formula will help us find any term in the sequence based on its position \( n \).
02
Calculate the First Term
To find the first term (\( a_1 \)), substitute \( n = 1 \) into the formula: \[ a_1 = 2(1) - 3 = 2 - 3 = -1. \] Thus, the first term is \( -1 \).
03
Calculate the Second Term
To find the second term (\( a_2 \)), substitute \( n = 2 \) into the formula: \[ a_2 = 2(2) - 3 = 4 - 3 = 1. \] Thus, the second term is \( 1 \).
04
Calculate the Third Term
To find the third term (\( a_3 \)), substitute \( n = 3 \) into the formula: \[ a_3 = 2(3) - 3 = 6 - 3 = 3. \] Thus, the third term is \( 3 \).
05
Calculate the Fourth Term
To find the fourth term (\( a_4 \)), substitute \( n = 4 \) into the formula: \[ a_4 = 2(4) - 3 = 8 - 3 = 5. \] Thus, the fourth term is \( 5 \).
06
Calculate the Fifth Term
To find the fifth term (\( a_5 \)), substitute \( n = 5 \) into the formula: \[ a_5 = 2(5) - 3 = 10 - 3 = 7. \] Thus, the fifth term is \( 7 \).
07
Calculate the 50th Term
To find the 50th term (\( a_{50} \)), substitute \( n = 50 \) into the formula: \[ a_{50} = 2(50) - 3 = 100 - 3 = 97. \] Thus, the 50th term is \( 97 \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Term Calculation
Calculating terms in an arithmetic sequence revolves around plugging different values into a given formula. For the sequence with the formula \( a_n = 2n - 3 \):
- Start by identifying the position \( n \) of the term you want to find.
- Substitute \( n \) into the formula.
- Perform the arithmetic operation: multiply \( 2 \) by \( n \) and then subtract \( 3 \).
This method allows you to calculate any term easily. For example, if you need to find the 10th term, substitute \( n = 10 \) in the formula: \( a_{10} = 2(10) - 3 = 17 \). This process underpins how arithmetic sequences operate, showing that each term is formed from a linear transformation of its position.
- Start by identifying the position \( n \) of the term you want to find.
- Substitute \( n \) into the formula.
- Perform the arithmetic operation: multiply \( 2 \) by \( n \) and then subtract \( 3 \).
This method allows you to calculate any term easily. For example, if you need to find the 10th term, substitute \( n = 10 \) in the formula: \( a_{10} = 2(10) - 3 = 17 \). This process underpins how arithmetic sequences operate, showing that each term is formed from a linear transformation of its position.
Sequence Formula
The sequence formula defines the pattern of the sequence. In our specific case, the formula is \( a_n = 2n - 3 \). This formula shows two vital components:
- Linear growth: The term \( 2n \) indicates that as \( n \) increases, each term in the sequence increases linearly by 2. This regular increment ensures a consistent pattern.
- Constant adjustment: The minus 3 adjusts each term by a fixed amount, shifting the entire sequence downward by 3 units.
Mathematics Education
Teaching arithmetic sequences involves illustrating basic principles of linear relationships. It's crucial to:
- Encourage students to recognize patterns in sequences via hands-on practice. Observing the incremental changes between terms reinforces understanding.
- Explain the function of each part of a formula, like distinguishing between the multiplier and constant, to demystify the math involved.
- Provide varied examples, such as increasing and decreasing sequences, to enhance comprehension.