College Algebra 7th Edition

Published by Brooks Cole
ISBN 10: 1305115546
ISBN 13: 978-1-30511-554-5

Chapter 3, Polynomial and Rational Functions - Section 3.2 - Polynomial Functions and Their Graphs - 3.2 Exercises - Page 303: 52

Answer

(a) $x$-intercepts: $0$ and $4.5$ $y$-intercept: $0$ (b) relative minimum is at $(3, -3)$ relative maximum is at $$(0, 0)$

Work Step by Step

(a) The $x$-intercepts can be found by looking at the points where the graph touches/crosses the $x$-axis. However, one of the $x$-intercepts is between two integers. To find the exact value of the $x$-intercepts, fund it algebraically by setting $P(x)=0$ then solving for $x$: \begin{align*} \frac{2}{9}x^3-x^2&=0\\ x^2\left(\frac{2}{9}x-1\right)&=0\\ \end{align*} Use the Zero-Product Property by equating each factor to zero, then solve each equation to obtain: \begin{align*} x^2&=0 &\text{or}& &\frac{2}{9}x-1=0\\\\ x&=0 &\text{or}& &\frac{2}{9}x=1\\\\ x&=0 &\text{or}& &\frac{9}{2}\cdot \frac{2}{9}x=1\cdot \frac{9}{2}\\\\ x&=0 &\text{or}& &x=\frac{9}{2} \end{align*} Thus, the $x$-intercepts are: $0$ and $4.5$ The graph crosses the $y$-axis at $(0,0)$. Thus, the $y$-intercept is $0$. (b) The graph has a relative maximum at $(0,0)$ and a relative minimum at $(3, -3)$.
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