Find the interval in which the function concave up??

The graph of the function http://www7.0zz0.com/2009/05/03/22/585474959.jpg

is concave up on the interval:

(-infinity,infinity)

None

(1,infinity)

(-infinity,0)U(1,infinity)

(0,infinity)

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I solve the question and my answer is :

The graph is concave up on (-infinity,-0.5)U(0,infinity)

and I'm sure from my answer but my answer is not included in the choices

and When I use the graphics calculator the graph is concave up on all interval

http://www7.0zz0.com/2009/05/03/22/140871664.jpg

So what is the correct answer??