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: 49

Answer

Zero: $\dfrac{1}{3}$ $x$-intercept: $\dfrac{1}{3}$

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 $P(x)=0$: $$9x^2-6x+1=0$$ Comparing $9x^2-6x+1=0$ to $ax^2+bx+c=0$ to find $a,b \text{ and } c$ $$\therefore a = 9, b=-6 , c =1$$ Evaluating the discriminant $b^2-4ac$ $$b^2-4ac = (-6)^2-4 \times 9 \times 1 = 0$$ Since the discriminant is equal to zero, then there is a real repeated root. The quadratic formula is given by: $$x= \dfrac{-b \pm \sqrt{b^2-4ac}}{2a}$$ $$x= \dfrac{6\pm \sqrt{0}}{2\times 9}$$ $$x=\dfrac{6\pm 0}{18}$$ $\therefore x =\dfrac{1}{3}$
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