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Ch. 8 - Sequences, Induction, and Probability
Blitzer - College Algebra 8th Edition
Blitzer8th EditionCollege AlgebraISBN: 9780136970514Non è quello che usi tu?Cambia libro di testo
Capitolo 9, Problema 33

Find each indicated sum. ∑k=15k(k+4)\(\sum\)_{k=1}^{5} k(k+4)

Guida verificata passo dopo passo
1
Identify the sum notation: you need to find the sum of the expression \(k(k+4)\) as \(k\) goes from 1 to 5, which is written as \(\sum_{k=1}^{5} k(k+4)\).
Expand the expression inside the summation: \(k(k+4) = k^2 + 4k\).
Rewrite the sum as the sum of two separate sums: \(\sum_{k=1}^{5} (k^2 + 4k) = \sum_{k=1}^{5} k^2 + \sum_{k=1}^{5} 4k\).
Use the properties of summation to factor out constants: \(\sum_{k=1}^{5} 4k = 4 \sum_{k=1}^{5} k\).
Calculate each sum separately using formulas: \(\sum_{k=1}^{n} k = \frac{n(n+1)}{2}\) and \(\sum_{k=1}^{n} k^2 = \frac{n(n+1)(2n+1)}{6}\), then substitute \(n=5\) and add the results.

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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. The expression 5Σk=1 means to sum the terms as k goes from 1 to 5. Understanding this notation is essential to correctly evaluate the sum.
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Interval Notation

Evaluating Polynomial Expressions

Each term in the sum involves evaluating the polynomial k(k+4) for each integer k from 1 to 5. This requires substituting values of k into the expression and simplifying before summing the results.
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Evaluating Algebraic Expressions

Properties of Finite Sums

Finite sums can be broken down into sums of simpler expressions, such as sums of k and sums of constants. Using properties like linearity of summation helps simplify calculations by separating and summing individual parts.
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Change of Base Property