Question 942429
1. Yes. Multiplication of two numbers in [0,1] always returns a number in [0,1].
2. No. For example, 0.1 - 0.8 = -0.7 which is not in [0,1].
3. f(x) is a function if and only if each x in the domain is mapped to exactly one value/output in the codomain.
4. Function notation (read "f of x") for a function f that takes argument x
For 3. and 4., see https://en.wikipedia.org/wiki/Function_(mathematics))