As $x\to -\infty $ , $f\left( x \right)\to 0.$
Work Step by Step
If the horizontal asymptote is $y=a$ then the function tends to $a$ as $x$ tends to $+\infty $ or $-\infty $. In the graph $y=0$ is a horizontal asymptote. So, the function $f\left( x \right)$ tends to $0$ as $x$ tends to $-\infty $.