Which of the following is a polynomial function in factored form with zeros at -2,5,and 8?
a. f(x)=(x-2)(x+5)(x+8)
b. f(x)=x^3+11x^2+14x-80
c. f(x)=x^3-11x^2+14+80
d. f(x)=(x+2)(x-5)(x-8)