PLEASE help I have been stuck on this for hours!
If a person starts to learn y items in x hours as given by y=21(x^2)^1/3 find the rate of learning for a person at the end of three hours.
I start out like this 1/3(21)(x^2)^-3/2
so 7(x^2)^-3/2
but now I am stuck and I don't know if what I did above was correct. Please help!

Question

PLEASE help I have been stuck on this for hours!
If a person starts to learn y items in x hours as given by y=21(x^2)^1/3 find the rate of learning for a person at the end of three hours. 
I start out like this 1/3(21)(x^2)^-3/2
so 7(x^2)^-3/2
but now I am stuck and I don't know if what I did above was correct. Please help!

aaronq · Answer

take the derivative which is the rate or slope (whatever you wanna call it)

aaronq · Answer

then plug in x=3 since 3 hours

anonymous · Answer

Yes, but how do you solve the derivative?

aaronq · Answer

www.wolframalpha.com

they have step by step

anonymous · Answer

Hint: You need to simplify first.  y=21(x^2)^1/3=21x^2/3 unless i am reading this wrong.  Then this becomes a very simple derivative.  If you cant solve it let me know.

anonymous · Answer

Here is a picture of the equation if that would help

anonymous · Answer

The derivative of 21X^2/3=2/3(21)x^-1/3=14X^-1/3 0r 14/x^1/3 so at x=3, this is goint to equal 14/3^1/3