Intermediate Algebra: Connecting Concepts through Application

Published by Brooks Cole
ISBN 10: 0-53449-636-9
ISBN 13: 978-0-53449-636-4

Chapter 8 - Radical Functions - 8.4 Solving Radical Equations - 8.4 Exercises - Page 654: 45

Answer

No solution

Work Step by Step

Given \begin{equation} \sqrt{2 x+3}=1-\sqrt{x+5}. \end{equation} First square both sides of the radical equation to eliminate the radical sign on the left. Rearrange thequation and square both sides again to eliminate the radical sign on the right hand side and then solve for $x$. \begin{equation} \begin{aligned} \sqrt{2 x+3}&=1-\sqrt{x+5}\\ \left( \sqrt{2 x+3}\right)^2&= \left( 1-\sqrt{x+5}\right)^2\\ 2 x+3& = 1-2\sqrt{x+5}+x+5\\ 2x-x+3-6& = -2\sqrt{x+5}\\ x-3 & = -2\sqrt{x+5}\\ \left(x-3\right)^2& = \left(-2\sqrt{x+5}\right)^2\\ x^2-6x+9&= 4x+20\\ x^2-10x-11&=0. \end{aligned} \end{equation} Use the quadratic formula to find the value(s) of $x$. \begin{equation} \begin{aligned} a&x^2+bx+c=0\\ a &= 1\ , b= -10\ ,\ c = -11\\ x & = \frac{-b\pm\sqrt{b^2-4ac}}{2a}\\ x&=\frac{-(-10) \pm \sqrt{(-10)^2-4 \cdot 1 \cdot(-11)}}{2 \cdot 1} \\ &= \frac{10\pm 12}{2}\\ \implies x& = \frac{10- 12}{2}\\ & = -1\\ x& = \frac{10+12}{2}\\ & = 11. \end{aligned} \end{equation} Check \begin{equation} \begin{aligned} \sqrt{2\cdot (-1)+3}& \stackrel{?}{=} 1-\sqrt{-1+5} \\ 1& \stackrel{?}{=}-1\quad \textbf{False}\\ \sqrt{2\cdot (11)+3}& \stackrel{?}{=} 1-\sqrt{11+5} \\ 5& \stackrel{?}{=}-3\quad \textbf{False}\ \end{aligned} \end{equation} The equation has no real solution.
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