Answer:
(6x+7)(6x-7)
Explanation:
Why this is, is because of the positive and negative sign in the expression.
With a positive and a negative it will cancel something.
36x^2-42x+42x-49. The -42x and the +42x cancel out because the are added together to get 0 so your answer is.
(6x+7)(6x-7).