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-2x2-5x=-50

 Sep 12, 2017
 #1
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+2

-2x^2 - 5x = -50       multiply through by -1

 

2x^2  + 5x  = 50      complete the square on x

 

2 [x ^2  +  (5/2)x ]  = 50       divide both sides by 2

 

x^2  +  (5/2)x     = 25         take (1/2)  of (5/2)  = 5/4.....square this = 25/16,  and add to both sides 

 

x^2  + (5/2)x  + 25/16  =   25  +  25/16         factor the left side and simplify the right

 

[ x +  5/4 ] ^2   =   [ 400 + 25]  / 16          take both roots

 

x + 5/4  =  ±√ [ 425]  / 4

 

x + 5/4  =   ±5√17 / 4       subtract 5/4 from both sides

 

x  = ±5√17 / 4  - 5/4  =  [  -5  ± 5√17 ] / 4  

 

 

cool cool cool

 Sep 12, 2017

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