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avatar+78 

Find all values of x such that \(\sqrt{4x^2} - \sqrt{x^2} = 6\)

 

Please help me asap! I appreciate your help!

 

CPhill said that it is:

sqrt (4x^2) - sqrt (x^2)  = 6       we can write

 

2sqrt (x^2)  - sqrt (x^2)  =  6

 

sqrt (x^2) = 6     square both sides

 

x^2  =  36      take both roots

 

x = ± 6

 

When i put in the answer, the website said that 6 is incorrect. Can anybody clarify/ tell me the new answer?

 Nov 3, 2018
 #1
avatar+17332 
+2

A little different approach might work:

 

sqrt (4x^2) =  +- 2x

sqrt(x^2)    = +- x

 

so it could be

-2x-x = 6       x= -2

-2x+x = 6      x = -6

2x-x = 6         x= 6

2x+x = 6       x = 2       2 and -2 won't work, but 6 and -6 should work

 Nov 4, 2018
edited by ElectricPavlov  Nov 4, 2018
 #2
avatar+78 
0

Thanks so much! It was correct this time....

 Nov 10, 2018

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