<h2>
Hello!</h2>
The answers are:
a) 
b) 
<h2>Why?</h2>
First, we need to know that for this case:

So,


We must add
to the expression in order to form a perfect square trinomial,

Writing the trinomial as a binomial square:

Have a nice day!
17/10-(2/5x2/2)
17/10-4/10
=13/10
I believe that the answer is 2.