+0  
 
+1
166
7
avatar+1318 

Help Me please.

 

Equations: solve for x

 

x4+x2-20=0

ManuelBautista2019  Mar 5, 2018
 #2
avatar+1318 
+1

But i think the answer is this:

 

-2,2,i√5,-i√5

is this correct?

ManuelBautista2019  Mar 5, 2018
 #3
avatar+92382 
+1

x^4   + x^2 - 20  =  0      factor

 

(x^2 + 5) (x^2 - 4)  = 0

 

(x^2 + 5)  ( x - 2) ( x + 2)  = 0

 

Set each factor to 0...and solve for x

 

x  - 2  = 0       x +  2  = 0       x^2 + 5  = 0

x  =  2             x  =  -2           x^2  =  -5         take both roots

                                              x = ±√-5

                                              x  = ±√5 i

 

So....the solutions are

 

x  =   { -2, 2, √5 i ,  - √5 i    }

 

 

 

cool cool cool

CPhill  Mar 5, 2018
 #4
avatar+1318 
+1

do I have to include the brackets in my answer?

ManuelBautista2019  Mar 5, 2018
 #5
avatar+92382 
0

No....I just did that for convenience, Manuel....your solutions are correct  !!!

 

 

cool cool cool

CPhill  Mar 5, 2018
 #6
avatar+1318 
+1

Thank you Cphill

 

You are a Math saver!!

ManuelBautista2019  Mar 5, 2018
 #7
avatar+92382 
0

HAHAHA!!!!....don't know about that...but...I do know a few answers, here and there...

 

 

cool cool cool

CPhill  Mar 5, 2018

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