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Hi there,

 

I'm having trouble solve for x in this equation.

I've checked the equation a few times, it's correct!

 

I appreciate your help!

 Oct 25, 2018
 #1
avatar+102320 
+1

Here's my  best attempt :

 

0   =    w         ( L^2x^2     -   x^4      -  7L^4  )

         ____        ______        ___         _____

         EI6L           2                 4             60

 

Multiply both sides by   EI6L / w     and the lead term "disappears"

 

0  =   L^2 x^2     -   x^4     -  7L^4

        ______         ____      _____

             2                4            60

 

Multiply through by  - 60

 

15x^4  -  30L^2x^2  +  7L^4   =   0

 

15x^4  -  30L^2x^2     =  -  7L^4         factor  out 15

 

15 ( x^4 - 2L^2x^2)  = - 7L^4            divide both sides  by 15

 

x^4  - 2L^2x^2   =     - 7L^4 / 15

 

Take  1/2  of 2L^2  = L^2

Square this  = L^4

Add to both sides

 

x^4 - 2L^2 x^2  + L^4  =   -7L^4 / 15   + L^4   

 

Factor the left side   and simplify

 

( x^2  - L^2)^2  =   8L^4 / 15

 

Take both roots  and simplify

 

x^2  - L^2  =   ±√ [ (8L^4 / 15) ]

 

x^2 - L^2  =  ±2L^2√ [ 2/15 ]

 

Add L^2  to both sides

 

x^2  =  L^2  ± 2L^2√ [ 2/15 ]

 

Take both roots again

 

x =  ±√ ( L^2 ± 2L^2√ [ 2/15 ]  )  =    ± L√ ( 1 ± 2√ [ 2/15 ]  ) 

 

 

cool cool cool

 Oct 25, 2018
edited by CPhill  Oct 25, 2018
edited by CPhill  Oct 25, 2018
edited by CPhill  Oct 25, 2018
edited by CPhill  Oct 25, 2018
 #2
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+1

how b****y painful.

 

thank you!

 Oct 25, 2018

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