For f (x) = x² - 3x - 9 and g (x) = x - 7, find (f - g) (x).

We know that According to Algebra of Real Functions:

If f and g are two real functions which are defined under the same domain then (f - g) (x) = f (x) - g (x)

Given f (x) = x² - 3x - 9 and g (x) = x - 7

⇒ (f - g) (x) = f (x) - g (x)

⇒ (f - g) (x) = x² - 3x - 9 - (x - 7)

⇒ (f - g) (x) = x² - 3x - 9 - x + 7

⇒ (f - g) (x) = x² - 4x - 2