standard_description: Relate the domain of a function to its graph and, where applicable, to the quantitative relationship it describes.  For example, if the function h(n) gives the number of person-hours it takes to assemble n engines in a factory, then the positive integers would be an appropriate domain for the function.
problem_activity: Write the formula for the functions depicted by the graphs below.
$${f(x)=}$$
$${g(x)=}$$
$${h(x)=}$$
[IMG]


aligns: yes