1/36 - c^2

This is a difference of squares, in the form of $$a^2 - b^2 = (a-b)(a+b)$$.

Here, $$a^2 = 1/36$$, so $$a = 1/6$$. Also, $$b^2 = c^2$$, so $$b=c$$.

Thus, the factored form is $$(1/6 - c)(1/6 + c)$$.