(x + 9) (x - 9)
follow the FOIL method
first
x(x) = x^2
outside
x(-9) = -9x
inside
9(x) = 9x
last
9(-9) = -81
x² - 9x + 9x - 81
simplify: x² - 81
x² - 81 is your answer
hope this helps
it is not - 18, because you are multiplying, not adding, and even if you are adding, the answer wouldn't have a -18
hope this helps
