Exercises 88–90 will help you prepare for the material covered in the next section. Use the formula an = a₁3(n-1) to find the seventh term of the sequence 11, 33, 99, 297,...
Table of contents
- 0. Review of Algebra4h 18m
- 1. Equations & Inequalities3h 18m
- 2. Graphs of Equations1h 43m
- 3. Functions2h 17m
- 4. Polynomial Functions1h 44m
- 5. Rational Functions1h 23m
- 6. Exponential & Logarithmic Functions2h 28m
- 7. Systems of Equations & Matrices4h 5m
- 8. Conic Sections2h 23m
- 9. Sequences, Series, & Induction1h 22m
- 10. Combinatorics & Probability1h 45m
9. Sequences, Series, & Induction
Geometric Sequences
Problem 1
Textbook Question
Write the first five terms of each geometric sequence. a1 = 5, r = 3
Verified step by step guidance1
Identify the first term \(a_1\) and the common ratio \(r\) of the geometric sequence. Here, \(a_1 = 5\) and \(r = 3\).
Recall the formula for the \(n\)-th term of a geometric sequence: \(a_n = a_1 \times r^{n-1}\).
Calculate the second term \(a_2\) by substituting \(n=2\) into the formula: \(a_2 = 5 \times 3^{2-1} = 5 \times 3\).
Calculate the third term \(a_3\) by substituting \(n=3\): \(a_3 = 5 \times 3^{3-1} = 5 \times 3^2\).
Continue this process to find the fourth and fifth terms: \(a_4 = 5 \times 3^{4-1}\) and \(a_5 = 5 \times 3^{5-1}\).
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Geometric Sequence Definition
A geometric sequence is a list of numbers where each term after the first is found by multiplying the previous term by a constant called the common ratio. This ratio remains the same throughout the sequence, creating a consistent pattern of growth or decay.
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Common Ratio (r)
The common ratio is the fixed factor by which each term in a geometric sequence is multiplied to get the next term. In this problem, the ratio is 3, meaning each term is three times the previous term, which determines how quickly the sequence grows.
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Finding Terms of a Geometric Sequence
To find the nth term of a geometric sequence, use the formula a_n = a_1 * r^(n-1), where a_1 is the first term and r is the common ratio. Applying this formula allows you to calculate any term, including the first five terms as requested.
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