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avatar+62 

find all real numbers (a) that satisfy \(\frac{1}{a^3 + 7} -7 = \frac{-a^3}{a^3 + 7}\).

 

thanks !

 May 11, 2020
 #1
avatar+111326 
+1

Rearrange  as

 

  1             a^3

_____ + _______  =    7

a^3+ 7     a^3 + 7

 

1 + a^3

______  =     7             cross-multiply

a^3 + 7

 

1 + a^3  = 7 ( a^3 + 7)

 

a^3  + 1  =  7a^3  + 49       subtract   49, a^3  from both sides

 

-48  =  6 a^3       divide both sides by  6

 

-8  = a^3           take  the cube oot of both sides

 

-2  =  a

 

 

cool cool cool

 May 11, 2020
 #2
avatar+62 
+1

thank you cphill ! :)

andrewstanells  May 11, 2020
 #3
avatar+111326 
0

OK, andrew    !!!

 

cool cool cool

CPhill  May 11, 2020

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