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avatar+26387 
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Solve \(\large \sqrt{x+14-8\sqrt{x-2}} + \sqrt{x+23-10\sqrt{x-2}} = 3\)

 

Substitute: \(\begin{array}{|rcll|} \hline \mathbf{ y } &=& \mathbf{\sqrt{x-2}} \qquad \text{or} \qquad y^2 &=& x-2 \\ \mathbf{ x } &=& \mathbf{y^2+2} \\ \hline \end{array} \)

 

\(\begin{array}{|rcll|} \hline \sqrt{x+14-8\sqrt{x-2}} + \sqrt{x+23-10\sqrt{x-2}} &=& 3 \\\\ \sqrt{y^2+2+14-8y} + \sqrt{y^2+2+23-10y} &=& 3 \\\\ \sqrt{y^2-8y+16} + \sqrt{y^2-10y+25} &=& 3 \\\\ && \boxed{ y^2-8y+16 = (y-4)^2=(4-y)^2} \\ && \boxed{ y^2-10y+25 = (y-5)^2=(5-y)^2} \\ \hline \end{array} \)

 

\(\begin{array}{|lrcll|} \hline \text{Case }1: \\ & y^2-8y+16 = (y-4)^2 \\ & y^2-10y+25 = (y-5)^2 \\ \hline & \sqrt{(y-4)^2} + \sqrt{(y-5)^2 } &=& 3 \\\\ & y-4 + y-5 &=& 3 \\\\ & 2y-9 &=& 3 \\\\ & 2y &=& 9+3 \\\\ & 2y &=& 12 \\\\ & \mathbf{y} &=& \mathbf{6} \\ \hline \end{array} \begin{array}{|lrcll|} \hline \text{Case }2: \\ & y^2-8y+16 = (y-4)^2 \\ & y^2-10y+25 = (5-y)^2 \\ \hline & \sqrt{(y-4)^2} + \sqrt{(5-y)^2 } &=& 3 \\\\ & y-4 + 5-y &=& 3 \\\\ & \mathbf{1} &\ne& \mathbf{3} \qquad \text{no solution!} \\ \hline \end{array}\\ \begin{array}{|lrcll|} \hline \text{Case }3: \\ & y^2-8y+16 = (4-y)^2 \\ & y^2-10y+25 = (5-y)^2 \\ \hline & \sqrt{(4-y)^2} + \sqrt{(5-y)^2 } &=& 3 \\\\ & 4-y + 5-y &=& 3 \\\\ & -2y+9 &=& 3 \\\\ & 2y &=& 9-3 \\\\ & 2y &=& 6 \\\\ & \mathbf{y} &=& \mathbf{3} \\ \hline \end{array} \begin{array}{|lrcll|} \hline \text{Case }4: \\ & y^2-8y+16 = (4-y)^2 \\ & y^2-10y+25 = (y-5)^2 \\ \hline & \sqrt{(4-y)^2} + \sqrt{(y-5)^2 } &=& 3 \\\\ & 4-y + y-5 &=& 3 \\\\ & \mathbf{-1} &\ne& \mathbf{3} \qquad \text{no solution!} \\ \hline \end{array}\\\)


\(\begin{array}{|rcll|} \hline \text{First solution}: \\ y= 6 \\ \hline x &=& y^2+2 \\ x &=& 6^2+2 \\ \mathbf{x} &=& \mathbf{38} \\ \hline \end{array} \begin{array}{|rcll|} \hline \text{Second solution}: \\ y= 3 \\ \hline x &=& y^2+2 \\ x &=& 3^2+2 \\ \mathbf{x} &=& \mathbf{11} \\ \hline \end{array}\)

 

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Jul 31, 2020
 #1
avatar+33661 
+2
Jul 31, 2020
 #1
avatar+12531 
0
Jul 31, 2020
 #2
avatar+310 
0
Jul 31, 2020
 #1
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0

 

At a concession​ stand,three hot dog(s) and two hamburger(s) cost ​$8.25​;two hot dog(s) and three hamburger(s) cost ​$8.00. Find the cost of one hot dog and the cost of one hamburger. What is the cost of one hot dog​?  

 

                                                              3 Dogs + 2 Burgers = 8.25    (1)  

                                                              2 Dogs + 3 Burgers = 8.00    (2)  

 

Multiply equation (1) by 2                       6D + 4B = 16.50                    (3)  

Multiply equation (2) by 3                       6D + 9B = 24.00                    (4)  

 

Subtract equation (3) from (4)                        5B  =  7.50  

Divide both sides by 5                                       B  =  1.50   One Burger costs $1.50  

 

Substitute 1.50 for B in (1)                      3D + (2)(1.50)  =  8.25  

                                                                3D + 3.00         =  8.25  

Subtract 3.00 from both sides                                    3D  =  5.25  

Divide both sides by 3                                                  D  =  1.75   One Dog costs $1.75  

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Jul 31, 2020
Jul 30, 2020
 #8
avatar+479 
+1
Jul 30, 2020

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