Intermediate Algebra: Connecting Concepts through Application

Published by Brooks Cole
ISBN 10: 0-53449-636-9
ISBN 13: 978-0-53449-636-4

Chapter 4 - Quadratic Functions - Chapter Review Exercises - Page 400: 39

Answer

The solutions are $x = 0$, $x = -5$, and $x = -2$.

Work Step by Step

First, we factor out what is common in both terms: $x(x^2 + 7x + 10) = 0$ To factor this equation, we want to find which factors, when multiplied, will give us the product of the $a$ and $c$ terms but when added together will give us the $b$ term. Let's look at possible factors: $5$ and $2$ $10$ and $1$ The first combination will work. Let's write the equation in factor form: $x(x + 5)(x + 2) = 0$ According to the zero product property, if the product of factors equals $0$, then each of the factors can be $0$; therefore, we can set each of these factors equal to $0$ and solve. Let's set the first factor equal to $0$: $x = 0$ For the second factor, we subtract $5$ from each side of the equation: $x = -5$ For the third factor, we subtract $2$ from each side of the equation: $x = -2$ The solutions are $x = 0$, $x = -5$, and $x = -2$. To check our answers, we substitute each of these values into the original equation to see if the two sides equal one another. Let's look at the first factor: $(0)^3 + 7(0)^2 + 10(0) = 0$ Evaluate exponents first: $0 + 7(0) + 10(0) = 0$ Multiply to simplify: $0 + 0 - 0 = 0$ Add first two terms: $0 - 0 = 0$ Subtract: $0 = 0$ The two sides of the equation are equal to one another; therefore, this solution is correct. Let's check the second solution: $(-5)^3 + 7(-5)^2 + 10(-5) = 0$ Evaluate exponents first: $-125 + 7(25) + 10(-5) = 0$ Multiply to simplify: $-125 + 175 - 50 = 0$ Add first two terms: $50 - 50 = 0$ Subtract: $0 = 0$ The two sides of the equation are equal to one another; therefore, this solution is correct. Let's check the third solution: $(-2)^3 + 7(-2)^2 + 10(-2) = 0$ Evaluate exponents first: $-8 + 7(4) + 10(-2) = 0$ Multiply to simplify: $-8 + 28 - 20 = 0$ Add first two terms: $20 - 20 = 0$ Subtract: $0 = 0$ The two sides of the equation are equal to one another; therefore, this solution is correct.
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