Question

Which function f(x) increases on the interval (-∞, 0) but decreases on the interval (0, -∞)?
A. f(x) = x^3
B. f(x) = -x^3
C. f(x) = x^4
D. f(x) = -x^4

Answer 1

If I may help?

Answer 2

You can take the first derivative of the function and then test points such as x=-1000 and x=1000.