Precalculus (6th Edition) Blitzer

Published by Pearson
ISBN 10: 0-13446-914-3
ISBN 13: 978-0-13446-914-0

Chapter P - Review Exercises - Page 144: 131

Answer

The solution of the equation $3{{x}^{2}}-7x+1=0$ is $x=\frac{7+\sqrt{37}}{6}$ or $x=\frac{7-\sqrt{37}}{6}$.

Work Step by Step

Consider the provided equation $3{{x}^{2}}-7x+1=0$ Compare the equation $3{{x}^{2}}-7x+1=0$ with the standard form of the binomial equation $a{{x}^{2}}+bx+c=0$. Thus, $\begin{align} & a=3 \\ & b=-7 \\ & c=1 \end{align}$ Use the quadratic formula, $x=\frac{-b\pm \sqrt{{{b}^{2}}-4ac}}{2a}$ , $\begin{align} & x=\frac{-\left( -7 \right)\pm \sqrt{{{\left( -7 \right)}^{2}}-4\left( 3 \right)\left( 1 \right)}}{2\left( 3 \right)} \\ & =\frac{7\pm \sqrt{49-12}}{6} \\ & =\frac{7\pm \sqrt{37}}{6} \end{align}$ Further simplification gives: $x=\frac{7+\sqrt{37}}{6}$ or $x=\frac{7-\sqrt{37}}{6}$. Check: Substitute $x=\frac{7+\sqrt{37}}{6}=2.18$ in the original equation $3{{x}^{2}}-7x+1=0$. $\begin{align} 3{{\left( 2.18 \right)}^{2}}-7\left( 2.18 \right)+1\overset{?}{\mathop{=}}\,0 & \\ 14.26-15.26+1\overset{?}{\mathop{=}}\,0 & \\ 14.26-14.26\overset{?}{\mathop{=}}\,0 & \\ 0=0 & \\ \end{align}$ Thus, verified. Substitute $x=\frac{7-\sqrt{37}}{6}=0.152$ in the original equation $3{{x}^{2}}-7x+1=0$. $\begin{align} 3{{\left( 0.152 \right)}^{2}}-7\left( 0.152 \right)+1\overset{?}{\mathop{=}}\,0 & \\ 0.064-1.064+1\overset{?}{\mathop{=}}\,0 & \\ 0.064-0.064\overset{?}{\mathop{=}}\,0 & \\ 0=0 & \\ \end{align}$ Thus, verified. Hence, the solution set is $\left\{ \frac{7+\sqrt{37}}{6},\frac{7-\sqrt{37}}{6} \right\}$.
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