Which function has exactly one zero? f(x)=x2−9

f(x)=x2+4x+4

f(x)=x2−4(x+3)

f(x)=5(x+6)(x−6)

Describe the end behavior of the function below. f(x)=(2/3)^x-2 a. as x increases, f(x) approaches infinity. b. as x decreases, f(x) approaches 2. c. as x increases, f(x) approaches -2. d. as x decreases, f(x) approaches negative infinity.