# intervals of increase and decrease

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• Feb 22nd 2010, 12:40 PM
jessee
intervals of increase and decrease
I need a bit of help here, I'm trying to figure out the intervals of increase and decrease, max and min points, intervals of concavity and any points of inflection for f(x)=x^3-x^2+4x-3, but I can't get through the increase and decrease intervals.
I know to find the intervals I have to find when the first derivative equals zero, but thats exactly where I'm stuck.
3x^2-2x+4=0; there's no common factor and I can't find a number for x that will make the equation equal 0.
help please?
• Feb 22nd 2010, 01:51 PM
ione
Quote:

Originally Posted by jessee
I need a bit of help here, I'm trying to figure out the intervals of increase and decrease, max and min points, intervals of concavity and any points of inflection for f(x)=x^3-x^2+4x-3, but I can't get through the increase and decrease intervals.
I know to find the intervals I have to find when the first derivative equals zero, but thats exactly where I'm stuck.
3x^2-2x+4=0; there's no common factor and I can't find a number for x that will make the equation equal 0.
help please?

That is because $f'(x)$ is never 0. I will be either be always positive or always negative. You need to determine which one.