And so let's figure out what the slope of the secant line is between four comma f of four and six comma f of six. And if it's equal to five, then we could use the mean value theorem. If it's not equal to five, then the mean value theorem would not apply. And so let's do that. F of six minus f of four, all of that over six minus four is equal to seven minus three over two, which is equal to two. So two not equal to five, so mean value theorem doesn't apply. Apply.