GIVEN:
We are given the expression;

Required;
To determine the constant term that must be added to the expression to make it a perfect square.
Step-by-step solution;
To make the expression a perfect square, we begin by taking the coefficient of x and dividing this by 2. Next we square the result. This is shown below;

Our new expresssion now becomes;

Therefore,
ANSWER:
The constant that must be added is 49.