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 3.5 - Complex Zeros and the Fundamental Theorem of Algebra - 3.5 Exercises - Page 330: 51

Answer

$x\displaystyle \in\left\{\frac{1- \sqrt {3}i}{2}. \frac{1+ \sqrt {3}i}{2}, 2 \right\}$

Work Step by Step

See The Rational Zero Theorem: If $\displaystyle \frac{p}{q}$ is a zero of the polynomial $f$ with integer coefficients, then $p$ is a factor of the constant term, $a_{0}$, and $q$ is a factor of the leading coefficient, $a_{n}$. ------------------------ $f(x)=x^{3}-3x^{2}+3x-2$ a. Candidates for zeros, $\frac{p}{q}:$ $p:\qquad \pm 1, \pm 2$ $q:\qquad \pm 1$ $\displaystyle \frac{p}{q}:\qquad \pm 1, \pm2$ b. Try for $x=2:$ $\begin{array}{lllll} \underline{2}| & 1 & -3 & 3 & -2\\ & & 2 & -2 & 2\\ & -- & -- & -- & --\\ & 1 & -1 & 1 & |\underline{0} \end{array}$ $2$ is a zero, $f(x)=(x-2)(x^{2} -x+1)$ c. Solve for the trinomial using the quadratic formula for the quadratic equation of $ax^2+bx+c$, $x=\frac{-b \pm \sqrt {b^2-4ac}}{2a}$. in this case, $x^2-x+1$, $x=\frac{1 \pm \sqrt {-1^2-4\times 1\times 1}}{2\times 1}=\frac{1\pm \sqrt {3}i}{2}$ $x\displaystyle \in\left\{\frac{1- \sqrt {3}i}{2}. \frac{1+ \sqrt {3}i}{2}, 2 \right\}$
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