Question 84302
You can use the following formula to solve such questions

(a + b)(a - b) = {{{a^2- b^2}}}

so,

(x + 6) (x - 6) = {{{x^2 - 6^2}}} = {{{x^2 - 36}}}

Check :

(x + 6)(x - 6) 
= {{{x*(x - 6) + 6*(x - 6)}}}

               = {{{x^2 - 6*x + 6*x - 36}}}
               = {{{x^2 -36}}}