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: 73

Answer

$\left\{3,11\right\}$

Work Step by Step

Squaring both sides, the given equation, $ \sqrt{2x+3}=2+\sqrt{x-2} ,$ is equivalent to \begin{align*} \left(\sqrt{2x+3}\right)^2&=\left(2+\sqrt{x-2}\right)^2 \\ 2x+3&=\left(2+\sqrt{x-2}\right)^2 \\ 2x+3&=(2)^2+2(2)\left(\sqrt{x-2}\right)+\left(\sqrt{x-2}\right)^2 &(\text{use }(a+b)^2=a^2+2ab+b^2) \\ 2x+3&=4+4(\sqrt{x-2})+x-2 \\ (2x-x)+(3-4+2)&=4(\sqrt{x-2}) \\ x+1&=4\sqrt{x-2} .\end{align*} Squaring both sides again, the equation above is equivalent to \begin{align*} (x+1)^2&=\left(4\sqrt{x-2}\right)^2 \\ (x)^2+2(x)(1)+(1)^2&=\left(4\sqrt{x-2}\right)^2 &(\text{use }(a+b)^2=a^2+2ab+b^2) \\ x^2+2x+1&=16\left(x-2\right) \\ x^2+2x+1&=16x-32 \\ x^2+(2x-16x)+(1+32)&=0 \\ x^2-14x+33&=0 .\end{align*} Using factoring of trinomials, the equation above is equivalent to \begin{align*} (x-11)(x-3)&=0 .\end{align*} Equating each factor to zero (Zero Product Property) and solving for the variable, then \begin{array}{l|r} x-11=0 & x-3=0 \\ x=11 & x=3 \end{array} Checking by substituting the solutions in the given equation results to \begin{array}{l|r} \text{If }x=11: & \text{If }x=3: \\\\ \sqrt{2(11)+3}\overset{?}=2+\sqrt{11-2} & \sqrt{2(3)+3}\overset{?}=2+\sqrt{3-2} \\ \sqrt{22+3}\overset{?}=2+\sqrt{9} & \sqrt{6+3}\overset{?}=2+\sqrt{1} \\ \sqrt{25}\overset{?}=2+3 & \sqrt{9}\overset{?}=2+1 \\ 5\overset{\checkmark}=5 & 3\overset{\checkmark}=3 .\end{array} Since all solutions satisfy the given equation, then the solution set of the equation $ \sqrt{2x+3}=2+\sqrt{x-2} $ is $\left\{3,11\right\}$.
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