Intermediate Algebra (12th Edition)

Published by Pearson
ISBN 10: 0321969359
ISBN 13: 978-0-32196-935-4

Chapter 8 - Section 8.3 - Equations Quadratic in Form - 8.3 Exercises - Page 530: 44

Answer

$t=\dfrac{3}{4}$

Work Step by Step

Squaring both sides of the given equation, $ 4t=\sqrt{8t+3} ,$ results to \begin{align*}\require{cancel} (4t)^2&=\left(\sqrt{8t+3}\right)^2 \\ 16t^2&=8t+3 \\ 16t^2-8t-3&=0 .\end{align*} Using factoring of trinomials, the equation above is equivalent to \begin{align*} (4t-3)(4t+1)&=0 .\end{align*} Equating each factor to zero (Zero Product Property) and solving for the variable, then \begin{array}{l|r} 4t-3=0 & 4t+1=0 \\ 4t=3 & 4t=-1 \\\\ t=\dfrac{3}{4} & t=-\dfrac{1}{4} .\end{array} Checking the solutions by substitution in the given equation results to \begin{array}{l|r} \text{If }t=\dfrac{3}{4}: & \text{If }t=-\dfrac{1}{4}: \\\\ 4\left(\dfrac{3}{4}\right)\overset{?}=\sqrt{8\left(\dfrac{3}{4}\right)+3} & 4\left(-\dfrac{1}{4}\right)\overset{?}=\sqrt{8\left(-\dfrac{1}{4}\right)+3} \\\\ \cancelto14\left(\dfrac{3}{\cancelto14}\right)\overset{?}=\sqrt{\cancelto28\left(\dfrac{3}{\cancelto14}\right)+3} & \cancelto14\left(-\dfrac{1}{\cancelto14}\right)\overset{?}=\sqrt{\cancelto28\left(-\dfrac{1}{\cancelto14}\right)+3} \\\\ 3\overset{?}=\sqrt{6+3} & -1\overset{?}=\sqrt{-2+3} \\ 3\overset{?}=\sqrt{9} & -1\overset{?}=\sqrt{1} \\ 3\overset{\checkmark}=3 & -1\ne1 .\end{array} Since $t=-\dfrac{1}{4}$ does not satisfy the original equation, then the only solution of the equation $ 4t=\sqrt{8t+3} $ is $t=\dfrac{3}{4}$.
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