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x^4-46x^2+45=0

 May 19, 2017
 #1
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x^4 - 46x^2 + 45 = 0

 

Let u = x^2

 

u^2 - 46u + 45 = 0

 

This factorises;  (u - 1)(u - 45) = 0

 

So 1)  u = 1       2) u = 45

 

Hence 1) x^2 = 1   so  1a) x = 1    and   1b) x = -1

 

and      2) x^2 = 45   so  2a)  x = sqrt(45) , x = sqrt(9*5),  x = 3sqrt(5)   and   2b)  x = -3sqrt(5)

.

 May 19, 2017
edited by Alan  May 19, 2017

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