Question says about what number can you add to
to get a rational number.
We know that rational numbers are the numbers which are written in form of p/q where p and q both are integers.
but q can never be 0.
If we add only some integer or real number to
then we will still get irrational number which is not of the form p/q.
so the only way to finish the radical part is to use the opposite of that
which is -
As you can see that
-
= 0
and we know that 0 is a rational number because that can be written as 0/1 in p/q form.
Hence final answer is -