See if this helps:
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Somebody please help me on this question, I really need help.
Continued here
http://web2.0calc.com/questions/please-help_65
I am sorry but i do not understand your hint.
Here's a more detailed solution:
+118609 
![Let $f$ be defined by \[f(x) = \left\{ \begin{array}{cl} 3-x & \text{ if } x \leq 3, \\ -x^3+2x^2+3x & \text{ if } x>3. \end{array} \right.\] Calculate $f^{-1}(0)+f^{-1}(6)$.](/api/ssl-img-proxy?src=http%3A%2F%2Fdata.artofproblemsolving.com%2Faops20%2Flatex%2Fimages%2F5488810e07ddad30fa1f47cccdcdb9ce71f6a01f.png)
