Answer:
9 - 441
Explanation:
I think you are missing digits in the problem, and this is what you meant:
(3 – 21)(3 + 21) =
Of course, you can do the operations in the parentheses first.
= (-18)(24)
= -432
Maybe what the problem wants you to do is to use the product of a sum and a difference.
(a - b)(a + b) = a² - b²
(3 – 21)(3 + 21) =
= 3² - 21²
= 9 - 441