I can't figure this interval out.

Let find:

for _____?

for _____?

for the derivative I got .

I set that to zero to find the critical points, and found

For I got

For I got

I was told that these are incorrect, and I don't understand why. I even graphed the derivative and this looked to me to be correct. Am I close? Please let me know where I am wrong. I really appreciate it. Thanks.

Re: I can't figure this interval out.

perhaps because you used instead of (notice the ] replaced with ) ).at f'(x) is 0, it shouldnt be included as a value for which f'(x) > 0.

Same reasoning for your interval for f'(x) < 0

Re: I can't figure this interval out.

Thanks a ton jakncoke, I would gladly buy you one given the chance.

Re: I can't figure this interval out.

I think you missed one critical point, that is where f'(x) is undefined. which is when x=0. So if you evaluate the first derivative test. The function is decreasing at (0,sqrt(1/6)) and increasing at (sqrt(1/6),infinity) because remember that any value of x less than or equal to zero is now allowed to be used as a critical point. Try this one out and hope this helps! :D