"f" is a set and it has a few points, "f" is also a function, or we can say that "f" is a function that we can graph with many points and each point has an x-coordinate and a y-coordinate, so each point is a (x,y) pair on the function "f".
the first argument in the pair is the value of the "independent" variable, for this case we can call it "x", and the second argument is the "dependent" variable, for this case we can call it "y".
so after all that mumble jumble, what is f(2) asking?
well, is asking, "when x = 2, what's 'y'?
hmmm let's look at the set, it has a pair of (2 , 2), meaning x = 2 and y = 2, well, there you have it f(2) = 2.
let me do "a, c and f" only.
[tex]f=\left\{(2,2) ~~,~~(-2,1)~~,~~\left(3,\frac{2}{3} \right) ~~,~~(\pi ,1)\right\} \\\\\\ \boxed{a}\qquad f(2)=2\qquad \qquad \boxed{f}\qquad f(\pi )=1 \\\\[-0.35em] ~\dotfill\\\\ g=\left\{(2,1)~~,~~(-3,-1)~~,~~\left( \frac{2}{3},-1 \right)\right\} \\\\\\ \boxed{c}\qquad g\left( \frac{2}{3} \right)=-1[/tex]
other way to read that is the coordinates of the set "g" are (x , g(x) ), and they're a point lieing on the graph of the function g(x).
