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: 34

Answer

The solutions are $x = -\frac{2}{3}$ and $x = 1$.

Work Step by Step

First, we want to rewrite this equation as a quadratic one. The quadratic equation is given as: $ax^2 + bx + c$, where $a$, $b$, and $c$ are all real numbers. To do this, we subtract $2$ from each side of the equation: $3x^2 - x - 2 = 0$ 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: $-3$ and $2$ $-6$ and $1$ The first combination will work. Let's rewrite the equation by splitting the middle term using the factors we found: $3x^2 - 3x + 2x - 2 = 0$ Group the the first two terms and the second two terms: $(3x^2 - 3x) + (2x - 2) = 0$ Factor out a $3x$ from the first group and a $2$ from the second group: $3x(x - 1) + 2(x - 1) = 0$ Group the coefficients together to make one factor whereas the other factor is the common factor: $(3x + 2)(x - 1) = 0$ According to the zero product property, if the product of two factors equals $0$, then either factor can be $0$; therefore, we can set each of these factors equal to $0$ and solve: $3x + 2 = 0$ or $x - 1 = 0$ Let's look at the first factor: $3x + 2 = 0$ Subtract $2$ from each side of the equation: $3x = -2$ Divide each side of the equation by $3$: $x = -\frac{2}{3}$ Let's look at the second factor: $x - 1 = 0$ Add $1$ to each side of the equation to solve: $x = 1$ The solutions are $x = -\frac{2}{3}$ and $x = 1$. To check our answer, we substitute each of these values into the original equation to see if the two sides equal one another: $3(-\frac{2}{3})^2 - (-\frac{2}{3}) = 2$ Evaluate exponents first: $3(\frac{4}{9}) + \frac{2}{3} = 2$ Multiply to simplify: $\frac{12}{9} + \frac{2}{3} = 2$ Simplify the fraction: $\frac{4}{3} + \frac{2}{3} = 2$ Add: $\frac{6}{3} = 2$ Simplify the fraction: $2 = 2$ The two sides of the equation are equal to one another; therefore, this solution is correct. Let's check the other solution: $3(1)^2 - (1) = 2$ Evaluate exponents first: $3(1) - 1 = 2$ Multiply to simplify: $3 - 1 = 2$ Subtract: $2 = 2$ The two sides of the equation are equal to one another; therefore, this solution is correct.
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