And so what we need to test is, is four, the derivative of y with respect to x, equal to four times, I could write y, but instead of y, let's write four x. I'm gonna put everything in terms of x. So y is equal to four x. So instead of four y, I could write four times four x. All of that over x. Is this true? Well, that x cancels with that, and I'm gonna get four is equal to 16, which it clearly is not. And so this is not a solution.