Question

Can someone please help with parts D and E?

Answer 1

Part D is just asking for the value of the function f(a)..

Answer 2

But that doesn't exist, right?

Answer 3

Or is it supposed to be an interval between -2 and 4?

Answer 4

f(a) is just the value of the function at x=a, here the solid dot is at f(a)=4

Answer 5

Why is it 4 and not undefined?

We haven't learned this yet; I don't know why they put it on our homework.

Answer 6

f(x) = 4 for x>=a
f(x) = -2 for x<a

see the greater or equal, if you put 'a' in the function , you get f(a)=4

Answer 7

It would be undefined if there were say 2 open circles, so there is no f(a) value. Here there is the solid dot at f(a)=4

No calc, this is just reading the graph for values.

Answer 8

similar to this kind, f(3) is defined at f(3)=-5 , from that solid dot point.