To find the values of f(x) at each given value of x, draw a vertical line on each given value of x and check which value of y corresponds to that value of x using the graph of f(x).
The problem says that the function is an even function. This means that:
[tex]f(x)=f(-x)[/tex]
Then, the function for negative values of x is the same that the function evaluated on the corresponding positive values.
For x=-1, we know that:
[tex]f(-1)=f(1)[/tex]
From the graph, we can see that f(1)=1
Repeating this procedure for x=-3, -5 and -6 we find that:
[tex]\begin{gathered} f(-1)=f(1)=1 \\ f(-3)=f(3)=1 \\ f(-5)=f(5)=3 \\ f(-6)=f(6)=3 \end{gathered}[/tex]
