How do you factor ##36x^2 - 25##?

Use the difference of squares identity to find:

##36x^2-25 = (6x-5)(6x+5)##

The difference of squares identity can be written:

##a^2-b^2 = (a-b)(a+b)##

In the case of ##36x^2 - 25##, notice that ##36x^2 = (6x)^2## and ##25 = 5^2##, so we get:

##36x^2-25 = (6x)^2-5^2 = (6x-5)(6x+5)##