If using the method of completing the square to solve the quadratic equation x^2-18x-2=0x 2 −18x−2=0, which number would have to be added to "complete the square"?

Delbert keeps track of total of the total number of points he earns on homework assignments, each of which is worth 60 points. at the end of the semester he has 810 points. write an equation for delbert’s average homework score a in terms of the number of assignments n.