ANSWER
f(3) = -2
f is a function
EXPLANATION
To find the value of f when x = 3 from the graph we have to draw a vertical line from x = 3 to the graph:
And then a horizontal line from the point of the graph where the first line touches it, to the y-axis:
The value of y where the orange arrow meets the y-axis is the value of the function when x = 3.
We found that f(3) = -2
To know if f is a relation or a function we can do the vertical line test. It consists on drawing a vertical line and if that line touches the graph of f in more than one point then it is not a function:
Therefore f is a function.
