Domain: $(-\infty, +\infty)$ Range: $(-\infty, +\infty)$ Refer to the image below for the graph.
Work Step by Step
$f(x)=3x$ The x-intercept can be found by letting f(x)=0. Here, $0=3x$ $0=x$ Hence, 0 is the x-intercept, therefore we plot (0,0). However, we have already found the y-intercept, too. We have to find another point on the graph. We let x=1 Here, $f(x)=3\times 1$ $f(x)=3$ Therefore we plot (1, 3). By connecting these two points by a straight line, we get the graph. The domain is $(-\infty, \infty)$ as the function will "work" for all real x-values. (We can see the domain on the graph too. As for every x-value we will find a corresponding point on the graph.) The range is $(-\infty, \infty)$ as we will get all real y-values after substituting all real x-values in the function. (We can see the domain on the graph too. As for every y-value we will find a corresponding point on the graph.)