Given f(x)=x^3-4x^2-2. State the intervals on which f is increasing and on which f is decreasing.

Question

amistre64 · Answer

derive and set to 0

amistre64 · Answer

$$f' = 3x^2 -8x =0$$
$$x(3x-8)=0$$ $x=0,8/3 $ right?

amistre64 · Answer

then maybe this; but we gotta check to make sure that x=0 aint an inflectionin disguise

<.........0...........8/3...........>
      -          +              +
      -          -               +
------------------------
      +         -                +

anonymous · Answer

Wait, where are you getting the equation from?

amistre64 · Answer

its called a derivative; the first derivative tells you how the function is moving.... its slope at any given point

amistre64 · Answer

when the derivative =0 that means we are bending back on itself and changing direction ..usually.  but, an inflection in a graph can also show a 0 in the 1st derivative

amistre64 · Answer

but; 6x-8 aint =0  at x=0 so its a bender

amistre64 · Answer

i gues the long way would be to factor the equation if we can

amistre64 · Answer

i just assumed by the nature of the question that it was a derivative type question lol

amistre64 · Answer

http://www.wolframalpha.com/input/?i=x^3-4x^2-2 might help you see whats happenin with it

anonymous · Answer

I'm not up to calc yet :/ sorry...

anonymous · Answer

Helppppp....