2. The given expression is;

We want to make the expression a perfect square trinomial.
In other words, we want to "complete the square".
In order to complete the square, we need to make c to be equal to
the square of the coefficient of the first power term divided by twice the coefficient of the first power term.
In other words,

Here, b =2 and a =1, so;

Therefore, the value of c to be added to make the expression a perfect square is 1
4. We have to find c;

We know that; a = 1 and b = -11 , so ;

Therefore, the value of c to be added to make the expression a perfect square is 30.25