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- Aug 20th 2008, 05:54 PMsadieannWhats the domain?????
- Aug 20th 2008, 06:16 PMarbolis
The domain is all the $\displaystyle x$ that make $\displaystyle x(x-18)>0$.

- Aug 20th 2008, 06:19 PMsadieann
I know that..but i need the domain in interval notation of that function

- Aug 20th 2008, 06:25 PMChris L T521
- Aug 20th 2008, 06:25 PMarbolis
Ok. Note that $\displaystyle x(x-18)$ vanishes when x equals 0 or 18. Note also that $\displaystyle y=x(x-18)=x^2-18x$ is an equation of a parabola with a global minimum. That mean that $\displaystyle x(x-18)\geq 0$ when $\displaystyle x \in (-\infty,0]$ U $\displaystyle [18,+\infty,)$, that's your domain.

EDIT: I'm sorry in my first post, it should be "The domain is all the $\displaystyle x$ that make $\displaystyle x(x-18)\geq 0$." - Aug 20th 2008, 06:38 PMsadieann
Thank you so much man.

- Aug 20th 2008, 06:43 PMarbolis
A pleasure to help. I understand you were in a rush but when you have time, try to understand what I did and ask us if you don't understand. Good luck.