The range of the function f (x) =√x^2−4
is (−∞, −1) ∪ (1, ∞). To explain
why this is true, you have to do two things:
(a) Show that if f (x) = y for some x, then either y > 1 or y < −1.
(b) Show that if y < −1 or y > 1, then the equation f (x) = y has a solution in x.