What is the sum of all possible values of k for which x^2 + kx - 10x + 16 is the square of a binomial?

(x-4)^2 This is the squared binomial which results in a '+16' constant

x^2 -8x + 16

k-10 must = -8

k = 2

Oh yah...it could be (x+4)^2

x^2 +8x + 16

in this case k-10 = 8

k = 18 or k = 2 summed = 20