4. There are $m$ identical machines working together, requiring $m$ hours to complete a task. (1) Suppose the same task is completed by $x$ machines ($x$ is a positive integer not greater than $m$), find the functional relationship between the required time $y$ (hours) and the number of machines $x$; (2) Draw the graph of the function when $m=4$.
4.(1) $y=\frac{m^{2}}{x}, x$ is a positive integer not greater than $m$ (2) omitted