Question

Who knows the answer to this question?

Answer 1

Every function associates input values with output values. The domain of a function is the set of all the inputs the function accepts.

You will basically always find your function graphed with the inputs on the horizontal axis and the outputs on the vertical axis. This means that every point on the graph has coordinates $(x,f(x))$, and the domain is the set of all the x values.

The points on your red line have all coordinates $(d,70)$, where d starts from 0 and ranges up to 12. So, the domain of the function is $[0,12]$