Answer
${\text{Graph:}}$
Work Step by Step
$$\eqalign{
& y = {e^{ - x/2}} \cr
& {\text{The function is in the form }}f\left( x \right) = {e^{ax}}{\text{ with }}a = - \frac{1}{2} < 0,{\text{ then}} \cr
& {\text{the function is decreasing for all its domain.}} \cr
& {\text{Making a table of values we obtain:}} \cr} $$
\[\boxed{\begin{array}{*{20}{c}}
x&y \\
{ - 4}&{7.389} \\
{ - 3}&{4.481} \\
{ - 2}&{2.718} \\
{ - 1}&{1.648} \\
0&1 \\
1&{0.606} \\
2&{0.367} \\
3&{0.223} \\
4&{0.135}
\end{array}}\]
$$\eqalign{
& {\text{Ploting the points and joining them we obtain the following}} \cr
& {\text{graph:}} \cr} $$
