Answer:
a)

b)

Explanation:
When working with these type of problems, they give you a function, which in this case is
, and they give you what that function is equal to, it's value, which in this case is
.
- When working with letter a), the function is
, meaning all the variables in the expression will be -4.
- When working with letter b), the function is
, meaning all the variables in the expression will be 0.
First let's work with letter a), (-4).




Let's now work with letter b), (0).




Hope it helped,
BiologiaMagister