Answer
This statement does not make any sense.
Work Step by Step
Consider the fact that the graph decreases in an interval $\left( -\infty ,a \right)$ and increases in an interval $\left( a,\infty \right)$.
This means that the point $a$ is a critical point as after that point the nature of the graph is changed from decreasing to increasing.
This implies $f\left( a \right)$ is not a relative maximum.
If the graph is decreasing on $\left( -\infty ,a \right)$ and increasing on $\left( a,\infty \right)$ , then $f\left( a \right)$ must be a relative minimum.
Hence, this statement does not make any sense and $f\left( a \right)$ is a relative minimum.
