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Solve \(\displaystyle x + 4 = \sqrt{10 x + 96}\).


Squaring both sides gives \(\displaystyle x^{2} + 8 x + 16 = 10 x + 96\). The equation is quadratic setting it equal to zero gives \(\displaystyle x^{2} - 2 x - 80 = 0\). Factoring gives \(\displaystyle (x - 10)(x + 8)=0\) so the possible solutions are \(\displaystyle x = 10\) and \(\displaystyle x = -8\). Checking the solution \(\displaystyle x = 10\) in the original equation gives \(\displaystyle 14 = 14\). The solution checks, so \(\displaystyle x = 10\) is a true solution. Checking the solution \(\displaystyle x = -8\) in the original equation gives \(\displaystyle -4 = 4\). The solution does no check, so \(\displaystyle x = -8\) is an extraneous solution.

Download \(\LaTeX\)

\begin{question}Solve $x + 4 = \sqrt{10 x + 96}$.
    \soln{10cm}{Squaring both sides gives $x^{2} + 8 x + 16 = 10 x + 96$. The equation is quadratic setting it equal to zero gives $x^{2} - 2 x - 80 = 0$. Factoring gives $(x - 10)(x + 8)=0$ so the possible solutions are $x = 10$ and $x = -8$. Checking the solution $x = 10$ in the original equation gives $14 = 14$. The solution checks, so $x = 10$ is a true solution. Checking the solution $x = -8$ in the original equation gives $-4 = 4$. The solution does no check, so $x = -8$ is an extraneous solution. }

\end{question}

Download Question and Solution Environment\(\LaTeX\)
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HTML for Canvas
<p> <p>Solve  <img class="equation_image" title=" \displaystyle x + 4 = \sqrt{10 x + 96} " src="/equation_images/%20%5Cdisplaystyle%20x%20%2B%204%20%3D%20%5Csqrt%7B10%20x%20%2B%2096%7D%20" alt="LaTeX:  \displaystyle x + 4 = \sqrt{10 x + 96} " data-equation-content=" \displaystyle x + 4 = \sqrt{10 x + 96} " /> .</p> </p>
HTML for Canvas
<p> <p>Squaring both sides gives  <img class="equation_image" title=" \displaystyle x^{2} + 8 x + 16 = 10 x + 96 " src="/equation_images/%20%5Cdisplaystyle%20x%5E%7B2%7D%20%2B%208%20x%20%2B%2016%20%3D%2010%20x%20%2B%2096%20" alt="LaTeX:  \displaystyle x^{2} + 8 x + 16 = 10 x + 96 " data-equation-content=" \displaystyle x^{2} + 8 x + 16 = 10 x + 96 " /> . The equation is quadratic setting it equal to zero gives  <img class="equation_image" title=" \displaystyle x^{2} - 2 x - 80 = 0 " src="/equation_images/%20%5Cdisplaystyle%20x%5E%7B2%7D%20-%202%20x%20-%2080%20%3D%200%20" alt="LaTeX:  \displaystyle x^{2} - 2 x - 80 = 0 " data-equation-content=" \displaystyle x^{2} - 2 x - 80 = 0 " /> . Factoring gives  <img class="equation_image" title=" \displaystyle (x - 10)(x + 8)=0 " src="/equation_images/%20%5Cdisplaystyle%20%28x%20-%2010%29%28x%20%2B%208%29%3D0%20" alt="LaTeX:  \displaystyle (x - 10)(x + 8)=0 " data-equation-content=" \displaystyle (x - 10)(x + 8)=0 " />  so the possible solutions are  <img class="equation_image" title=" \displaystyle x = 10 " src="/equation_images/%20%5Cdisplaystyle%20x%20%3D%2010%20" alt="LaTeX:  \displaystyle x = 10 " data-equation-content=" \displaystyle x = 10 " />  and  <img class="equation_image" title=" \displaystyle x = -8 " src="/equation_images/%20%5Cdisplaystyle%20x%20%3D%20-8%20" alt="LaTeX:  \displaystyle x = -8 " data-equation-content=" \displaystyle x = -8 " /> . Checking the solution  <img class="equation_image" title=" \displaystyle x = 10 " src="/equation_images/%20%5Cdisplaystyle%20x%20%3D%2010%20" alt="LaTeX:  \displaystyle x = 10 " data-equation-content=" \displaystyle x = 10 " />  in the original equation gives  <img class="equation_image" title=" \displaystyle 14 = 14 " src="/equation_images/%20%5Cdisplaystyle%2014%20%3D%2014%20" alt="LaTeX:  \displaystyle 14 = 14 " data-equation-content=" \displaystyle 14 = 14 " /> . The solution checks, so  <img class="equation_image" title=" \displaystyle x = 10 " src="/equation_images/%20%5Cdisplaystyle%20x%20%3D%2010%20" alt="LaTeX:  \displaystyle x = 10 " data-equation-content=" \displaystyle x = 10 " />  is a true solution. Checking the solution  <img class="equation_image" title=" \displaystyle x = -8 " src="/equation_images/%20%5Cdisplaystyle%20x%20%3D%20-8%20" alt="LaTeX:  \displaystyle x = -8 " data-equation-content=" \displaystyle x = -8 " />  in the original equation gives  <img class="equation_image" title=" \displaystyle -4 = 4 " src="/equation_images/%20%5Cdisplaystyle%20-4%20%3D%204%20" alt="LaTeX:  \displaystyle -4 = 4 " data-equation-content=" \displaystyle -4 = 4 " /> . The solution does no check, so  <img class="equation_image" title=" \displaystyle x = -8 " src="/equation_images/%20%5Cdisplaystyle%20x%20%3D%20-8%20" alt="LaTeX:  \displaystyle x = -8 " data-equation-content=" \displaystyle x = -8 " />  is an extraneous solution. </p> </p>