Question 84164
Factor:
{{{27r^2-12s^2}}} First, factor out a 3.
{{{3(9r^2-4s^2)}}} Now, do you see that the parentheses contain the difference of two squares?
The difference of two squares can be factored thusly: {{{A^2-B^2 = (A-B)(A+B)}}}
Applying this to your problem:
{{{3(9r^2-4s^2) = 3(3r-2s)(3r+2s)}}} So...
{{{27r^2-12s^2 = 3(3r-2s)(3r+2s)}}}
Do you see how it works?