Let f(x) = 4x and g(x) = x + 6. What's
the smallest number that is in the domain of
fºg?

For this case we have the following functions:

By definition of composition of functions we have to:

So:

By definition, the domain of a function is given by all the values for which the function is defined. The compound functionis defined for all real numbers.

The domain of is given by all real numbers.

Domain ∈ (-∞,∞)