+0  
 
0
838
1
avatar+49 

Find all real numbers x such that \(\left(\dfrac{x}{3}\right)^3-3x^2+81x-729=25+2(5)(3)+9.\)

 Aug 27, 2017
 #1
avatar+94619 
+3

 

(x/3)^3 -3x^2 + 81x - 729  =  25 + 2(5)(3) +  9

 

Simplify the right side and note that the left side can be factored as : 

 

(x/3 - 9)^3   =  64     take the cube root of both sides

 

(x/3 - 9)  = 4      add 9 to both sides

 

x/3  =  13       multiply both sides by 3

 

x  = 39   .....this is the only real solution......

 

 

 

cool cool cool

 Aug 27, 2017

12 Online Users

avatar
avatar

New Privacy Policy

We use cookies to personalise content and advertisements and to analyse access to our website. Furthermore, our partners for online advertising receive information about your use of our website.
For more information: our cookie policy and privacy policy.