Determine the value(s) of k such that f(x) = −x^2 − 2x + k has one zero

Answer 1

From the quadratic formula:

x = (2±√(4+4k))/-2

To have only on zero, √(4+4k) must equal zero

4+4k = 0

k= -4/4 = -1

Then the one zero will be, x=-1