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Which of the following are solutions to the equation below?

 

Check all that apply.

 

x2 + x - 5 = 0

 

A.  \(x = {5 - \sqrt{21} \over 2}\)

 

B.  \(x = {5 + \sqrt{21} \over 2}\)

 

C.  \(x = {5 + \sqrt{29} \over 2}\)

 

D.  \(x = {-1 - \sqrt{21} \over 2}\)

 

E.  \(x = {5 - \sqrt{29} \over 2}\)

 

F.  \(x = {-1 + \sqrt{21} \over 2}\)

 Oct 14, 2019
 #1
avatar+104962 
+2

x^2 + x - 5  = 0

 

Let a  = 1      b  = 1    c   = -5

 

Using the quadratic formula  we have that

 

x =     -1 ±√ [ 1^2 - 4* 1 * -5 ]       =        -1  ± √ [1 + 20 ]            -1  ± √21

         ___________________              _____________    =     ________

                     2 * 1                                           2                              2

 

So  D, F    are the correct answers

 

 

cool cool cool

 Oct 14, 2019

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