Chapter 11: Problem 42
Evaluate each series. $$\sum_{i=3}^{6}\left(2 i^{2}+1\right)$$
Short Answer
Expert verified
176
Step by step solution
01
- Understand the Summation Notation
The summation notation \(\sum_{i=3}^{6}\left(2 i^{2}+1\right)\) means that you need to evaluate the expression \(2i^{2} + 1\) for each integer value of \(i\) from 3 to 6, and then find the sum of these values.
02
- Evaluate the Expression for Each Integer
Evaluate the expression \(2i^{2} + 1\) for each value of \(i\) from 3 to 6:For \(i = 3\), \(2(3)^{2} + 1 = 2 \times 9 + 1 = 19\)For \(i = 4\), \(2(4)^{2} + 1 = 2 \times 16 + 1 = 33\)For \(i = 5\), \(2(5)^{2} + 1 = 2 \times 25 + 1 = 51\)For \(i = 6\), \(2(6)^{2} + 1 = 2 \times 36 + 1 = 73\)
03
- Sum the Evaluated Values
Add the values obtained from Step 2:\(19 + 33 + 51 + 73\)Calculate the sum: \(19 + 33 = 52\)\(52 + 51 = 103\)\(103 + 73 = 176\)
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
series evaluation
Understanding how to evaluate a series is crucial in mathematics. A series is simply the sum of the terms of a sequence. In the given exercise, the series is expressed using summation notation: \(\sum_{i=3}^{6}\left(2 i^{2}+1\right)\). This notation tells us to calculate the expression \(2i^{2} + 1\) for each integer value of \(i\) from 3 to 6, and then sum up these results.
By breaking down the problem as outlined in the step-by-step solution, we can see exactly how the calculations are performed:
Finally, summing these values gives us the total of \(19 + 33 + 51 + 73 = 176\). This step-by-step method ensures clarity and accuracy in evaluating the series.
By breaking down the problem as outlined in the step-by-step solution, we can see exactly how the calculations are performed:
- For \(i = 3\), we get \(2(3)^{2} + 1 = 19\).
- For \(i = 4\), we get \(2(4)^{2} + 1 = 33\).
- For \(i = 5\), we get \(2(5)^{2} + 1 = 51\).
- For \(i = 6\), we get \(2(6)^{2} + 1 = 73\).
Finally, summing these values gives us the total of \(19 + 33 + 51 + 73 = 176\). This step-by-step method ensures clarity and accuracy in evaluating the series.
summation formula
Summation formulas can simplify the process of finding the sum of a series. For instance, the formula for the sum of the first \(n\) squares is given by:
\[ \sum_{k=1}^{n} k^2 = \frac{n(n+1)(2n+1)}{6} \]
However, in our exercise, we are not using such a direct formula. Instead, we evaluate each term individually within a specific range (from \(i = 3\) to \(6\)). Knowing different summation formulas can be very useful:
\[ \sum_{k=1}^{n} k^2 = \frac{n(n+1)(2n+1)}{6} \]
However, in our exercise, we are not using such a direct formula. Instead, we evaluate each term individually within a specific range (from \(i = 3\) to \(6\)). Knowing different summation formulas can be very useful:
- Arithmetic series: \[ \sum_{k=1}^{n} k = \frac{n(n+1)}{2} \]
- Geometric series with ratio \(r\): \[ \sum_{k=0}^{n} ar^k = a \frac{1-r^{n+1}}{1-r} \] (for \(r e 1\))
By applying appropriate summation formulas, you can significantly speed up the process of series evaluation in more complex problems.
integer sequence
An integer sequence is a list of numbers where each number is an integer. In our exercise, the integer sequence is implicitly given by the range of \(i\) values (from 3 to 6). Sequences can take various forms and be defined by different rules:
In the context of our exercise, we can notice that we are looking at expressions of the form \(2i^2 + 1\) for successive integers. Understanding these sequences helps in breaking down the problem and computing the overall sum more easily.
- Arithmetic sequence: each term is obtained by adding a constant to the previous term. Example: 2, 4, 6, 8, ...
- Geometric sequence: each term is found by multiplying the previous term by a fixed non-zero number. Example: 2, 6, 18, 54, ...
- Square sequence: the terms are the squares of integers. Example: 1, 4, 9, 16, ...
In the context of our exercise, we can notice that we are looking at expressions of the form \(2i^2 + 1\) for successive integers. Understanding these sequences helps in breaking down the problem and computing the overall sum more easily.