Chapter 4: Problem 4
Find the value of the indicated sum. \(\sum_{l=3}^{8}(l+1)^{2}\)
Short Answer
Expert verified
The value of the sum is 271.
Step by step solution
01
Understand the Expression
The given expression is a summation: \(\sum_{l=3}^{8}(l+1)^{2}\). This means we need to sum up values obtained by squaring \(l+1\) for each integer value of \(l\) from 3 to 8 inclusive.
02
Expand and Evaluate the Expression Inside the Summation
First rewrite the expression inside as \((l+1)^{2} = l^2 + 2l + 1\). We will evaluate this for each value of \(l\) from 3 to 8.
03
Calculate Individual Terms
Calculate \((l+1)^{2}\) for each integer \(l\) from 3 to 8:- For \(l=3\), \((3+1)^2 = 16\)- For \(l=4\), \((4+1)^2 = 25\)- For \(l=5\), \((5+1)^2 = 36\)- For \(l=6\), \((6+1)^2 = 49\)- For \(l=7\), \((7+1)^2 = 64\)- For \(l=8\), \((8+1)^2 = 81\)
04
Sum the Results
Add all the individual terms calculated:\(16 + 25 + 36 + 49 + 64 + 81\).
05
Compute the Final Sum
Perform the addition:\(16 + 25 + 36 + 49 + 64 + 81 = 271\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Summation notation
Summation notation is a way to represent the sum of a sequence of terms. It's denoted by the Greek capital letter Sigma (\( \Sigma \)), and it typically includes a formula to calculate each term in the sequence. Let's break down the notation used in this exercise:
- The notation \( \sum_{l=3}^{8} \) indicates we are summing from \( l = 3 \) to \( l = 8 \).
- Inside the summation, \( (l+1)^{2} \) is the expression you evaluate at each integer \( l \) within the range.
Polynomial expansion
The process of polynomial expansion involves rewriting expressions in an expanded form.
In our exercise, the term \( (l+1)^{2} \) is expanded as a polynomial:
In our exercise, the term \( (l+1)^{2} \) is expanded as a polynomial:
- First, rewrite the squared term: \( (l+1)^{2} = l^2 + 2l + 1 \).
- This is a basic example of a binomial expansion, where the expression is expanded into a sum of terms.
Step-by-step calculation
Breaking problems down into smaller, more manageable steps is a useful strategy in mathematics. This is particularly effective for complex summations, where each step builds on the last to reach a final solution.
Here's the approach used in this exercise:
Here's the approach used in this exercise:
- Identify the expression and rewrite it in a form that’s easy to calculate for each term \( (l+1)^{2} \to l^2 + 2l + 1 \).
- Calculate the expanded polynomial for each specific value of \( l \) in the summation range from 3 to 8.
- Sum all the individual results to find the total sum, checking each step for accuracy.
Summing term by term helps in understanding each part’s contribution to the overall result.