Control-drag (or type) $f\left(x\right)\=\dots$

Context Panel: Assign Function

The transparent green dot on the graph in Figure 1.1.1(a) is at the point $\left(1\,2\right)$, corresponding to the value $f\left(1\right)$ = $2$. If evaluation produces a real number, that real number is the limit. Hence,

The red circle at $\left(4\,8\right)$ indicates a gap in the function at $x\=4$ because $f\left(4\right)$ is undefined: a division-by-zero error occurs if the function is evaluated at $x\=4$. However, the graph suggests the estimate

a := 4:
H := [ 0.5, 0.1, 0.01, 0.001 ]:
xL := [seq( a-h, h=H )]:
xR := [seq( a+h, h=H )]:
header := < `x` | `f(x)` >,
< `_____` | `_______________` >:
bodyL := seq( < X | f(X) >, X= xL ):
tableL := < header, bodyL >:
bodyR := seq( < X | f(X) >, X= xR ):
tableR := < header, bodyR >:
tableL, tableR;