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