Answer
See below.
Work Step by Step
We either draw the graph by hand or graph using technology.
Placing a pencil on the graph left of the line $x=a$ and tracing rightward towards $x=a$, we record the $y$-coordinates of the points of the graph. If the $y$-values approach approach a number $L_{1}$, we estimate $L_{1}$ as the left limit of the function at $x=a$. If they don't, we conclude that there is no left limit.
Similarly, from the right side of the graph, we either estimate $L_{2}$, the right limit, or we conclude that there is none.
If both one-sided limits exist and the equal the same number $L$, we say that $L$ is the limit of the function at $x=a$.
One disadvantage is that we may not be able to PRECISELY determine the limit.
