Or another way to say it, it's going to be decreasing when f prime of x is less than zero. So what is f prime of x? Well, we could use the derivative rules and derivative properties we know. We apply the power rule to x to the sixth. We bring the six out front or multiply the one coefficient here times six to get six x to the fifth, decrement that exponent, minus, bring the five times the three, minus 15 x to the, we decrement the five, so x to the fourth. And we need to figure out over what intervals is this going to be less than zero? And now let's see how we can simplify this a little bit.