can you help me? critical numbers

[mathhelp1a]

find all critical numbers
f(x) = x (2x+1)^ 1/2

is -1/3 and -1/2 the answers

 

[BigGlenntheHeavy]

Correct: See graph.

[attachment=0:3jniro2d]jkl.jpg[/attachment:3jniro2d]