Write a formula for the general term (the nth term) of each geometric sequence. Then use the formula for an to find a7, the seventh term of the sequence. 18, 6, 2, 2/3, ...
Ch. 8 - Sequences, Induction, and Probability

Chapter 9, Problem 21
Use the Binomial Theorem to expand each binomial and express the result in simplified form. (2x3 − 1)4
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Identify the binomial expression to be expanded: \((2x^{3} - 1)^4\).
Recall the Binomial Theorem formula: \(\displaystyle (a - b)^n = \sum_{k=0}^{n} \binom{n}{k} a^{n-k} (-b)^k\), where \(\binom{n}{k}\) is the binomial coefficient.
Set \(a = 2x^{3}\), \(b = 1\), and \(n = 4\). Write the expansion as \(\sum_{k=0}^{4} \binom{4}{k} (2x^{3})^{4-k} (-1)^k\).
Calculate each term by evaluating the binomial coefficient \(\binom{4}{k}\), raising \$2x^{3}\( to the power \)(4-k)\(, and multiplying by \)(-1)^k\( for \)k = 0, 1, 2, 3, 4$.
Simplify each term by applying the exponent to \(2\) and \(x^{3}\) separately, then combine like terms to write the final expanded polynomial.

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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Binomial Theorem
The Binomial Theorem provides a formula to expand expressions of the form (a + b)^n, where n is a non-negative integer. It states that (a + b)^n = Σ (n choose k) * a^(n-k) * b^k, summing k from 0 to n. This theorem simplifies the expansion process without multiplying the binomial repeatedly.
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Binomial Coefficients
Binomial coefficients, denoted as (n choose k), represent the number of ways to choose k elements from n and are calculated using factorials: n! / (k!(n-k)!). They serve as the coefficients in the expanded form of a binomial expression and determine the weight of each term.
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Exponent Rules
Exponent rules govern how to handle powers in algebraic expressions, such as multiplying powers with the same base by adding exponents and raising a power to another power by multiplying exponents. These rules are essential when expanding terms like (2x³)^m to simplify the expression correctly.
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