We want to figure out, I'll write it here, critical points. And just as a refresher of what critical points means, it's the points where the derivative of f of x is 0. So critical points are f prime of x is either equal to 0 or it's undefined. 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.