Precalculus: Concepts Through Functions, A Unit Circle Approach to Trigonometry (3rd Edition)

Published by Pearson
ISBN 10: 0-32193-104-1
ISBN 13: 978-0-32193-104-7

Chapter 2 - Linear and Quadratic Functions - Section 2.3 Quadratic Functions and Their Zeros - 2.3 Assess Your Understanding - Page 146: 35

Answer

Zeros: $\dfrac{-1+\sqrt{7}}{6}, \dfrac{-1-\sqrt{7}}{6}$ $x$-intercepts: $\dfrac{-1+\sqrt{7}}{6}, \dfrac{-1-\sqrt{7}}{6}$

Work Step by Step

To find the zeros of a function $g$, solve the equation $g(x)=0$ The zeros of the function are also the $x-$intercepts. Let $F(x)=0$: $$3x^2+x-\dfrac{1}{2}=0$$ Taking $3$ as a common factor: $$3\left(x^2+\dfrac{1}{3}x-\dfrac{1}{6}\right)=0$$ $$x^2+\dfrac{1}{3}x-\dfrac{1}{6}=0$$ Rearranging the Equation: $$x^2+\dfrac{1}{3}x=\dfrac{1}{6}$$ The coefficient of $x^2$ is 1 and that of $x$ is$ \dfrac{1}{3}$, complete the square by adding $\left(\dfrac{1 \times \dfrac{1}{3}}{2}\right)^2 = \dfrac{1}{36}$ $$\left(x^2+\dfrac{1}{3}x+\dfrac{1}{36}\right)=\dfrac{1}{6}+\dfrac{1}{36}$$ $$\left(x+\dfrac{1}{6}\right)^2 = \dfrac{7}{36}$$ $$\left(x+\dfrac{1}{6}\right)=\pm \dfrac{\sqrt{7}}{6}$$ $\therefore x+\dfrac{1}{6} = \dfrac{\sqrt{7}}{6} \hspace{20pt}\text{ or } \hspace{20pt} x+\dfrac{1}{6} = -\dfrac{\sqrt{7}}{6} $ Solve each equation to obtain the zeros of the function (which are the also the function's $x$-intercepts): $x+\dfrac{1}{6} = \dfrac{\sqrt{7}}{6} \to x=\dfrac{-1+\sqrt{7}}{6} $ $x+\dfrac{1}{6} = -\dfrac{\sqrt{7}}{6} \to x= \dfrac{-1-\sqrt{7}}{6}$
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