Question 197177
{{{36x^2-100}}} This is difference of 2 squares (36x^2 is 6x*6x) and 100 is 10*10.

Usually that would be enough to say 
{{{36x^2-100}}} =
{{{(6x -10)(6x+10)}}} and call is a day. But in this case, you can see that each term includes a common factor of 2.
{{{6x-10}}} = {{{2*(3x-5)}}} etc.
So 
{{{(6x -10)(6x+10)}}} 
{{{2*(3x-5) * 2*(3x+5)}}}
{{{4 *(3x-5)*(3x+5)}}}


Alternatively, you might have seen that 36 and 100 are both products of 2 squares.
36 = 9*4 
100 = 25*4
If you factor out the 4, you are still left with a difference of 2 squares
{{{4*(9x^2 - 25)}}}
Which simplifies to the same result.

All this just confirms that in mathematics, there are many ways to get to the same answer (hopefully correct) answer.

Hope that helps