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: 70

Answer

Zeros: $2,\dfrac{5}{3}$ $x$-intercepts: $2,\dfrac{5}{3}$

Work Step by Step

To find the zeros of a function $f$, solve the equation $f(x)=0$ The zeros of the function are also the $x-$intercepts. Let $H(x)=0$: $$3(1-x)^2+5(1-x)+2=0$$ Let $u=1-x$, the original equation becomes $$3u^2+5u+2=0$$ By factoring $$(u+1)(3u+2) = 0$$ Use the Zero-Product Property by equating each factor to zero, then solve each equation to obtain: \begin{align*} u +1&=0 &\text{ or }& &3u+2=0\\ u &=-1 &\text{ or }& &3u=-2\\ u &= -1 &\text{ or }& &u=-\dfrac{2}{3}\\ \end{align*} To solve for $x$, we use $u=1-x$ $$\because u = 1-x$$ $$\therefore x =1-u$$ For $u=-1$ $$x=1-(-1) $$ $$x= 2$$ For $u=-\dfrac{2}{3}$ $$x=1-(-\dfrac{2}{3})$$ $$x= \dfrac{5}{3}$$ $\therefore x =2,\dfrac{5}{3}$
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