Chapter 11: Problem 13
Evaluate. $$ \sum_{i=3}^{5} i(i+2) $$
Short Answer
Expert verified
The sum is 74.
Step by step solution
01
Understand the Problem
The problem asks to evaluate the sum of the expression \(i(i+2)\) from \(i = 3\) to \(i = 5\). This means we need to calculate the expression for each integer value of \(i\) between 3 and 5, and then find the resulting sum.
02
Evaluate for i = 3
Substitute \(i = 3\) into the expression \(i(i+2)\): \[3(3+2) = 3 \times 5 = 15\].
03
Evaluate for i = 4
Substitute \(i = 4\) into the expression \(i(i+2)\): \[4(4+2) = 4 \times 6 = 24\].
04
Evaluate for i = 5
Substitute \(i = 5\) into the expression \(i(i+2)\): \[5(5+2) = 5 \times 7 = 35\].
05
Calculate the Sum
Add the results from each step together to find the sum: \[15 + 24 + 35\]. Calculate this to get: \[15 + 24 = 39\]. Then, \[39 + 35 = 74\].
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Series Evaluation
In mathematics, a series refers to the sum of the terms of a sequence. In our specific problem, we are tasked with evaluating a particular series noted with the summation symbol, \(\sum\). This is known as summation notation. It's a shorthand way to express the addition of a sequence of numbers. In the given exercise, the series is represented as \(\sum_{i=3}^{5} i(i+2)\). This requires us to find the value of the expression \(i(i+2)\) for each integer \(i\) from 3 to 5, then sum up these values. Here's how the process generally works:
- Identify the expression to be evaluated, here it's \(i(i+2)\).
- Determine the range of the variable, from 3 to 5 in this example.
- Substitute each integer value within the range into the expression, compute it, and add them all together.
Algebraic Expressions
An algebraic expression combines numbers, variables, and arithmetic operations to represent a value. In our exercise, we have the expression \(i(i+2)\). Here, \(i\) is a variable that changes within a specified range (from 3 to 5). The structure of this expression indicates several operations:
- The variable \(i\) itself, representing our current point in the range.
- Addition inside the parentheses, \(i + 2\), which modifies the original variable.
- Multiplication of the modified variable \(i + 2\) by the original variable \(i\).
Mathematical Operations
In this exercise, we worked through several mathematical operations to arrive at the solution. The operations needed include:
- Substitution: Replacing the variable \(i\) with specific integer values from the range 3 to 5.
- Addition: Performed within the parentheses to calculate \(i + 2\) for each value of \(i\).
- Multiplication: After calculating \(i + 2\), we multiply the result by \(i\) to complete the evaluation of the expression.