a) So to find f(2) this means x=2, and you’re looking for y. On the graph, where x=2, y=3.
This means f(2)=3
b) To find f(x)=0, find where y=0. y=0 at x=5, and y=0 at x=-5.
Hope this makes sense!! If you have any more questions, let me know on the comments.
