Answer
The required solution for $ x=-1$ and $ x=-3$ is $ f\left( x \right)=1$.
Work Step by Step
From the graph one can see that when $ f\left( x \right)=1$ (that is, the y-coordinate is 1), the x values are $-1$ and $-3$.
Thus, the value of x for which $ f\left( x \right)=1$ is $ x=-1$ and $ x=-3$.
