Chapter 11: Problem 16
Evaluate. $$ \sum_{i=1}^{4} 3^{i-1} $$
Short Answer
Expert verified
The sum is 40.
Step by step solution
01
Understanding the Sigma Notation
Sigma notation, \( \sum_{i=1}^{4} 3^{i-1} \), is a way to represent a sum where \( i \) starts at 1 and ends at 4. For each value of \( i \), we substitute into \( 3^{i-1} \) and add the results.
02
Substitute and Calculate for Each Term
We will evaluate each term by substituting \( i \) from 1 to 4 into the expression \( 3^{i-1} \). - For \( i=1 \), it's \( 3^{1-1} = 3^0 = 1 \).- For \( i=2 \), it's \( 3^{2-1} = 3^1 = 3 \).- For \( i=3 \), it's \( 3^{3-1} = 3^2 = 9 \).- For \( i=4 \), it's \( 3^{4-1} = 3^3 = 27 \).
03
Sum All Calculated Values
Now, we add the calculated values from each term:\( 1 + 3 + 9 + 27 = 40 \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Exponential Expressions
Exponential expressions are a way to denote repeated multiplication of a number by itself. These expressions are written with two main components: a base and an exponent. The exponent tells us how many times to multiply the base by itself. For example, in the expression \(3^4\), 3 is the base, and 4 is the exponent, indicating that we should multiply 3 by itself four times: \(3 \times 3 \times 3 \times 3\).
- If the exponent is 0, any nonzero base raised to this power equals 1. This is why \(3^0 = 1\) in our exercise.
- An exponent of 1 simply indicates the base itself, so \(3^1 = 3\).
- Higher exponents imply further repeated multiplication, like \(3^2 = 9\) and \(3^3 = 27\).
Series Evaluation
Series evaluation involves calculating the sum of a sequence of terms. When you see sigma notation, such as \(\sum_{i=1}^{4} 3^{i-1}\), it signifies that we will sum a series of terms based on some formula. Here's how it works:
- The symbol \(\sum\) represents the process of summation.
- The expression under the sum tells us what formula to use for creating the sequence.
- The range of numbers below and above the sigma, \(i=1\) to 4, tells us the bounds for the index \(i\).
Mathematical Notation
Mathematical notation is a collection of symbols used to convey mathematical ideas and concepts succinctly and efficiently. In our exercise, sigma notation \(\sum\) plays this role by providing a concise way to represent the addition of a series of numbers. Here’s how it breaks down for this problem:
- The symbol \(\sum\) is the summation sign, indicating that a sum of terms follows.
- The limits of summation, \(i=1\) to 4, specify a "loop" where \(i\) takes each integer value from 1 through 4.
- The expression \(3^{i-1}\) is the formula used for each term in the series, depending on the value of \(i\).