Question 7765
Factor: {{{3x - 12x^3}}} 

First factor 3x:
  {{{3x(1 - 4x^2)}}} Notice that you now have, in the parentheses, a difference of two squares which can be factored: {{{(a^2 - b^2) = (a+b)(a-B)}}}, so:

{{{3x(1 - 4x^2) = 3x(1+2x)(1-2x)}}} Finally you have:

{{{3x - 12x^3 = 3x(1 + 2x)(1 -2x)}}}