Well, now we have an expression that tells us the slope of the tangent line, or you could view it as the instantaneous rate of change with respect to x for any x value. So if I were to say, if I were now to say f prime, let's say f prime of two, this would tell me what is the slope of the tangent line of our function when x is equal to two. And I do that by using this expression. So this is going to be five times two to the fourth plus six times two squared, six times two squared, minus two times two, minus two times two. And this is going to be equal to, let's see, two to the fourth power is 16, 16 times five is 80, so that's 80. And then this is six times four, which is 24. And then we are going to subtract four.