Precalculus (10th Edition)

Published by Pearson
ISBN 10: 0-32197-907-9
ISBN 13: 978-0-32197-907-0

Chapter 2 - Functions and Their Graphs - 2.2 The Graph of a Function - 2.2 Assess Your Understanding - Page 65: 28

Answer

a. YES b. If $x=0$, $f(0)=\frac{1}{2}$; The point on the graph is $(0,\frac{1}{2})$. c. $(0, \frac{1}{2})$ and $(2, \frac{1}{2})$ d. All real numbers except $x=-4$ e. no $x$ intercept f. $(0, \frac{1}{2})$

Work Step by Step

(a) The point $\left(1,\frac{3}{5}\right)$ is on the graph of $f$ if its coordinates satisfy the equation. $f(x)=\dfrac{x^2 +2}{x+4}$ $\dfrac{3}{5}=\dfrac{1^2 +2}{1+4}$ $\dfrac{3}{5}\stackrel{\checkmark}{=}\dfrac{3}{5}$ Thus, the $\left(1,\frac{3}{5}\right)$ is on the graph of $f$. (b) Substitute $0$ to $x$: $f(x)=\dfrac{x^2 +2}{x+4}$ $f(0)=\dfrac{0^2 +2}{0+4}$ $f(0)=\dfrac{1}{2}$ Therefore, the point on the graph is $\left(0,\frac{1}{2}\right)$ (c) Substitute $\frac{1}{2}$ to $f(x)$ then solve for $x$: $f(x)=\dfrac{x^2 +2}{x+4}$ $\dfrac{1}{2}=\dfrac{x^2 +2}{x+4}$ $x+4=2x^2 +4$ $4-4=2x^2-x$ $0=2x^2-x$ $0=x(2x-1)$ $x=0, \frac{1}{2}$ Therefore, the points on the graph are $\left(0, \frac{1}{2}\right)$ and $\left(2, \frac{1}{2}\right)$. (d) The given function is defined for all real numbers except $x=-4$ as it makes the denominator $0$. Thus, the domain is all real numbers except $x=-4$ (e) To find the $x$-intercept/s, set $y=0$ then solve for $x$. $y=\dfrac{x^2 +2}{x+4}$ $0=\dfrac{x^2 +2}{x+4}$ The equation has no solution since no value of $x$ will make $\dfrac{x^2+2}{x+4}$ equal to $0$. Therefore, there is no $x$ intercept in the given function . (f) To find the $y$-intercept, set $x=0$ then solve for $y$. $y=\dfrac{x^2 +2}{x+4}$ $y=\dfrac{0^2 +2}{0+4}$ $y=\dfrac{1}{2}$ Therefore, the $y$ intercept is $\left(0, \frac{1}{2}\right)$
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