simplify and state the restrictions on the variables.

Question

a^3/(a+1)^2 + a/(a+1)^2

Answer 1

There is a common denominator so you simply add them to get

(a^3 + a)/(a+1)^2

One of the basic restriction we have in arithmetic is that we cannot divide by zero
there are divisions of (a+1) in each of your terms, so you have to ask yourself,
"When is a+1 equal to zero"?

the answer is clearly a = -1

so the restriction is that a cannot be equal to -1