Let's look at the other tail:

graph looking at the eventual behavior of the upward tail  ... As x gets smaller and smaller, we are following the graph to the left.  As we do this, what's happening to the y values on the graph?  53... 725...  9280...  5,932,491  If Pierre was running on this thing, would he need mountain climbing equipment?

As x gets smaller and smaller, the height of the graph is going up, up, up.

As x approaches-infinity, the height of the graph approaches
infinity.  
Asx  -->  -infinity , f( x )  -->  infinity

To sum up:
 

graph of -x^3+ some x stuff  ...  as x  -->  -infinity  ,  f( x )  -->  infinity  ...  as x  -->  infinity  ,  f( x )  -->  -infinity