find the term that must be added to both sides of the equarion so that the equation can be solved by the method of completing the square

x^2 - 10x = -16

The term that must be added to both sides of the equation is (10/2)^2 = 25.

Adding 25 to both sides:
x^2 - 10x + 25 = -16 + 25
x^2 - 10x + 25 = 9

Now the equation can be solved by completing the square.