# Find the interval where function is increasing or decreasing

#### itchygo

So this is supposed to be basic problem. I can't find help anywhere online since they want to show if its increasing or decreasing based on a graph. The problem I'm now doesn't have a graph. It just gives me the function f(x)=3x+5. The derivative is just 3. With this information how do I know if it's increasing or decreasing on either side?

#### skeeter

Math Team
$f'(x)=3 > 0$ ... what does a derivative that is always positive tell you about the behavior of a function?

If you don't know, I recommend you research the topic more thoroughly.

1 person

#### itchygo

$f'(x)=3 > 0$ ... what does a derivative that is always positive tell you about the behavior of a function?

If you don't know, I recommend you research the topic more thoroughly.
A derivative that's always positive. Is it far fetched to say that that it can be increasing OR decreasing from either side?

#### skeeter

Math Team
A derivative that's always positive. Is it far fetched to say that that it can be increasing OR decreasing from either side?
Well, that response tells me you don't have a clue. Go to the link and find out for yourself what the sign of a function's derivative says about its behavior.

What does a derivative tell us about a function?