# How can I plot a function so that it indicates undefined point?

I tried to graph a function with an undefined point. The example is as below.

f[x_] = (x^2 + x -6) / (-4x^2 - 16x - 12);

Plot[f[x], {x, -3.1, -2.99}]


The output is a curve but there should be a hole ($x$ can't be $-3$) in the curve. Is there any setting in Plot that will show that the curve is undefined at $x = -3$?

• What's the problem? f[-3] = -2. Also use := not =. – David G. Stork Sep 1 '18 at 0:23

You can use Exclusions and ExclusionsStyle:
Plot[f[x], {x, -3.1, -2.99}, Exclusions -> True,

• Add in CapForm["Round"] for good measure. – Brett Champion Sep 1 '18 at 2:51