Chapter 11: Problem 52
Write the terms for each series. Evaluate the sum, given that \(x_{1}=-2, x_{2}=-1, x_{3}=0\) \(x_{4}=1,\) and \(x_{5}=2 .\) $$\sum_{i=1}^{5}-x_{i}$$
Short Answer
Expert verified
The sum is 0.
Step by step solution
01
Identify the Given Terms
List out the given terms for the series. We have the terms: \(x_{1} = -2\), \(x_{2} = -1\), \(x_{3} = 0\), \(x_{4} = 1\), and \(x_{5} = 2\).
02
Substitute and Apply the Summation
We need to find the sum \(\sum_{i=1}^{5} -x_{i}\). Substitute each \(x_i\) into the equation and apply the negative sign: \(\sum_{i=1}^{5} -x_{i} = -x_{1} - x_{2} - x_{3} - x_{4} - x_{5}\)
03
Insert the Values
Replace each \(x_i\) with its respective value: \(-(-2) - (-1) - (0) - (1) - (2) \)
04
Simplify the Expression
Evaluate the expression step-by-step: \(2 + 1 + 0 - 1 - 2 = 2 + 1 -1 -2 = 0\)
05
Calculate the Sum
Sum the final simplified values: \(2 + 1 - 1 - 2 = 0\)
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Summation Notation
Summation notation, represented by the Greek letter sigma \(\sum\), is a compact way to express the sum of a sequence of terms. In the format \(\sum_{i=1}^{n} a_i\), \(\sum\) signifies summation, \(\i=1\) represents the starting index (usually 1), and \(\) is the last value of the index. The expression \(\sum_{i=1}^{5} -x_{i}\) tells us to sum the terms from \(i=1\) to \(i=5\) of \(-x_i\). This notation helps to succinctly represent long sums and clarify operations on sequences.
To break it down:
To break it down:
- Sigma (Summation Symbol) – The \(\sum\) sign represents the sum of a series of terms.
- Index of Summation – \(\i\) starts at 1 and ends at 5 in our exercise.
- Expression – \(-x_i\), meaning we take the negative of each term in the series.
Arithmetic Series
An arithmetic series is the sum of the terms of an arithmetic sequence. An arithmetic sequence has a constant difference between consecutive terms. For instance, in our exercise we had values \(x_1 = -2 \, x_2 = -1 \, x_3 = 0 \, x_4 = 1 \, x_5 = 2\). These terms do not form an arithmetic sequence because their differences are not constant, but they can still be summed using summation notation.
Key takeaways about arithmetic series:
Key takeaways about arithmetic series:
- Consistent Difference – The difference between consecutive terms in an arithmetic sequence is always the same.
- Sum Formula – For a series, if we have \(n\) terms, the sum is given by \[S = \frac{n}{2} (a_1 + a_n)\], but only if it's truly an arithmetic series.
Series Evaluation
Series evaluation is the process of finding the sum of all the terms in a series. For \(\sum_{i=1}^{5} -x_{i}\), we followed these steps to evaluate:
- Identify the Terms: We list out the terms given: \(x_{1}=-2 \), \(x_{2}=-1 \), \(x_{3}=0 \), \(x_{4}=1 \), \(x_{5}=2\).
- Apply the Negative: Getting \(-x_{1}, -x_{2}, -x_{3}, -x_{4}, -x_{5}\) simplifies to \(2, 1, 0, -1, -2\).
- Simplify and Sum: Adding these values gives us \(\sum_{i=1}^{5} -x_{i} = 2 + 1 + 0 - 1 - 2 = 0\).
Precalculus Problem-Solving
Precalculus problem-solving often involves understanding and applying algebraic concepts to solve complex problems. This problem demonstrated how to:
- Recognize Patterns: Identify the terms in the series and understand the operations involved.
- Apply Mathematical Rules: Use summation notation and negative values correctly.
- Simplify Step-by-Step: Break down complex expressions into simpler parts to find the final result.