Question

The area (A) of a circle is a function of its radius (r) and is given by the function A = f(r) = πr2. What is the domain of this function?

a) all positive real numbers
b) all real numbers
c) all positive real numbers including 0
d) all real numbers excluding fractions

Answer 1

a) all positive real numbers
A = f(r) =πr2 is a quadratic function, it's domain are all real numbers but since we are talking about an area and an area can't be defined by negative number, the real domain of the function are all positive real numbers