Using a remarkable product you must factor the expression: f(x) =36x^2-324 and you are entitled to 5 steps

$$ f(x) = 36x^2-324\: $$ We know that square of 6x is 36x^2 and square of 18 is 324. $$ \left(6x\right)^2-\:\left(18\right)^2 $$ We know that, $$ a^2-b^2\:=\:\left(a+b\right)\left(a-b\right) $$ $$ \left(6x+18\right)\:\left(6x-18\right) $$ 6(x+3) 6(x-3) 36(x+3)(x-3) Factor of the expression $$ f(x) = 36x^2-324\: $$ is (6x + 18) (6x-18) or 36(x+3)(x-3)