i dont how to do this and i can't figure it out

Determine the x values where F(x) is positive

f(x)=x^(3)-9x

determine the x values where f(x) is increasing

f(x)=x^(2)-2x-8

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- Apr 27th 2009, 12:36 PMducktrixcollege algebra help
i dont how to do this and i can't figure it out

Determine the x values where F(x) is positive

f(x)=x^(3)-9x

determine the x values where f(x) is increasing

f(x)=x^(2)-2x-8 - Apr 27th 2009, 12:41 PMJameson
Hi ducktrix,

Welcome to MHF!

In the future please post one problem per thread and show all attempted work so we know what you know.

For #1, first factor this.

You should be able to tell that the three zeros of f(x) are 0, 3 and -3. So draw a number line and mark these three points on it. Now the regions inbetween these values will either be positive or negative. Choose a test point to see. Make sense?