This function looks differentiable everywhere, so the critical points that we're worried about are probably, well I can tell you, they're definitely just the points where f prime of x is going to be equal to 0. This derivative, f prime of x, is going to actually be defined over the entire domain. So let's actually write down the derivative right now. So the derivative of this, f prime of x, this is pretty straightforward, the derivative of 3x to the fourth, 4 times 3 is 12. 12x to the, we'll just decrement the 4 by 1, 3. You just multiply times the exponent and then decrease the new exponent by 1. Minus 3 times 4 is 12, times x to the, 1 less than 3 is 2.