Why do you say #y=x^2# decreases on the interval #(-oo, 0]#? Why is #0# included?

1 Answer
Jan 26, 2018

You don't, please read:

Explanation:

When writing interval notation of function, a "turning point" (where a function goes from increasing to decreasing, increasing to constant, constant to decreasing, etc.) is not included in the notation.

The function #y=x^2# decreases on the interval #(-oo, 0)# and increases in the interval #(0,oo)#.