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Ch. 5 - Integrals
Hass - Thomas' Calculus 15th Edition
Hass15th EditionThomas' CalculusISBN: 9780137616077Non è quello che usi tu?Cambia libro di testo
Capitolo 5, Problema 5.PE.3a

           10           10
Suppose that Σ aₖ = -2 and Σ bₖ = 25. Find the value of
           k = 1          k = 1


  10
a. Σ aₖ/4
  k = 1

Guida verificata passo dopo passo
1
Identify the given information: \( \sum_{k=1}^{10} a_k = -2 \) and \( \sum_{k=1}^{10} b_k = 25 \).
Understand that the problem asks for \( \sum_{k=1}^{10} \frac{a_k}{4} \), which means each term \( a_k \) is divided by 4 before summing.
Recall the property of summations that allows factoring out constants: \( \sum_{k=1}^{n} c \cdot a_k = c \cdot \sum_{k=1}^{n} a_k \), where \( c \) is a constant.
Apply this property to the given sum: \( \sum_{k=1}^{10} \frac{a_k}{4} = \frac{1}{4} \sum_{k=1}^{10} a_k \).
Substitute the known sum \( \sum_{k=1}^{10} a_k = -2 \) into the expression to write \( \sum_{k=1}^{10} \frac{a_k}{4} = \frac{1}{4} \times (-2) \).

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Concetti chiave

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Summation Notation (Sigma Notation)

Summation notation uses the Greek letter sigma (Σ) to represent the sum of a sequence of terms indexed by an integer variable. It concisely expresses adding terms like a₁ + a₂ + ... + aₙ. Understanding the limits of summation and the general term is essential for manipulating and evaluating sums.
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Properties of Summations

Summations have linearity properties, meaning the sum of a constant times a sequence equals the constant times the sum of the sequence. For example, Σ (c * aₖ) = c * Σ aₖ. This property allows factoring constants out of sums, simplifying calculations involving scaled sequences.
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Given Series Sums and Their Use

Knowing the total sums of sequences (like Σ aₖ = -2) allows direct substitution when evaluating related sums. This is useful when the problem asks for sums of scaled or transformed sequences, enabling quick computation without summing individual terms.
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Intro to Series: Partial Sums