What is the sum of all possible values of k for which x^2 + kx - 9x + 25 is the square of a binomial?

Answer 1

must be (x-5)(x-5) or (x+5)(x+5)
(x-5)^2 = x^2 -10 x + 25
k-9 = -10
k =-1
or
k-9 = +10
k = 19
19-1 = 18