+0  
 
0
654
1
avatar+49 

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

Jz1234  Aug 27, 2017
 #1
avatar+90023 
+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

CPhill  Aug 27, 2017

9 Online Users

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.