For what real values of c is x2−8x−14x+c the square of a binomial?
x^2 - 8x - 14x + c
x^2 - 22x + c
x^2 - 22x + (22/2)^2
x^2 - 22x + 11^2
x^2 - 22x + 121
( x - 11)^2
So c = 121
