Question

If a graph of a function is given by f(x) = x^3 – 9x, which statement is true?

a f(x) is increasing on the interval [-3,0]
b f(x) is decreasing on the interval [-3,0]
c f(x) is constant on the interval [-√3, √3]
d f(x) is decreasing on the interval [-√3, √3]