Bounded from Above
A function is bounded above if there is a real number, k, such that for all of x, f(x) ≤ k.
The number k is called the upper bound.
k = 0.135
Bounded from Below
A function is bounded below if there is a real number, k', such that for all of x, f(x) ≥ k′.
The number k' is called the lower bound.
k′ = 2
k′ ≤ f(x) ≤ k
k = ½ k′ = -½