Could someone and explain this to me

Step-by-step explanation:

Four

Start by trying to understand what f(x) means. First of all it is the same thing as y in the equation given in question 4. It is a shorthand that tells you that you put an x in wherever you see an x on the right.

More important, it tells you what to put in for x on the right.

f(z) would tell you to put z in for x anywhere there is an x on the right.

f(z)=2z+1. It is just a shorthand to tell you what to do on the right.

f(2) means put a 2 in for the x on the right. Read all of this carefully. You need to know it.

f(2) = 2(2) + 1

f(2) = 4 + 1

f(2) = 5

Five

f(x) = -x - 5            The minus 4 is not going to change what you do.

f(-4) = -(-4) - 5        Wherever you see an x you put in a minus 4

f(-4) = 4 - 5

f(-4) = - 1

Just so you know, consider a more complicated example

f(x) = 20x^3 + 7x^2 + 4x + 19

Where ever you see an x put in 2

f(2) = 20*(2^3) + 7*(2^2) + 4(2) + 19

f(2) = 20*8 + 7*4 + 4*2 + 19

f(2) = 160 + 28 + 8 + 19

f(2) = 215

Note x can be anything the question tells you it is.

f(5) means put a 5 in for every x.