So what's the derivative of v with respect to u? What is v prime of u of x? Well, we know, we know, let me actually write it right over here. If v of x is equal to seven to the x power, v prime of x would be equal to, and we proved this in other videos where we take derivatives, exponentials of bases other than e, this is going to be the natural log of seven, times seven to the x power. So if we are taking v prime of u of x, then notice, instead of an x everywhere, we're going to have a u of x everywhere. So this right over here, this is going to be natural log of seven times seven to the, instead of saying seven to the x power, remember, we're taking v prime of u of x. So it's going to be seven to the x squared minus x power.