Answer:
f(0) = 1
Explanation:
f(x) indicates the "output" value present at the "input" (Output referring to the y value and input referring to the x value). So f(0) would mean the "y" value present at x = 0; however, there are two circles at x = 0. One of the dots is open(hollow) meaning that the "x" and "y" values present there are excluded. This leaves the closed(filled) dot which means that value is included and is the answer.