Question 8434
   {{{3x^4-81x}}}

 = 3x {{{x^3 - 27}}}
 = 3x(x-3){{{(x^2 + 3x + 9)}}} [by using {{{x^3-a^3}}} = (x-a){{{(x^2+ ax +a^2)}}} ]

 Why nobody pointed out the mistake of another solution?

 Kenny