Alright, so here's the deal. I need to find the interval of this derivative function:
So far, I've gotten that the derivative is this:
f-prime(x)= -5x + 12
I tried to make the equation equal to zero. What happened was I got 2.4. Theoretically, anything below 2.4 should be increasing. Everything above 2.4 should be decreasing, I've even tested this.
But the site that I submit it to wants it in interval notation. That's great, but it won't read my interval notation. Am I wrong or is my notation wrong? If I am, what do I do with the derivative?