f(a)=b means that the graph contains the point (a,b)

So

f(2)=-3 means that the graph contains the point (2,-3)



We want to reflect that point through the origin, so first draw a line
(in red from that point up to the origin, like this:



Now continue that line the same distance on the other side of the
origin, like this:



Now can you figure out what that point is? If so, the answer will be
its y coordinate.


Edwin