Hi guys...I'm having some troubles with this one question and it's really starting to bug me cause I keep getting it wrong.

The question is:

So, I tried simplifying it...

v = (9*x^1/2 + 5/(3*x^1/3))^2

v = (9x^1/2 + 5/(3x^1/3))^2

I then distributed the 2 from outside the brackets into the brackets, so:

v = (81x + 25/9x^2/3)

Then I took the derivative...

v(der) = 81 + 25/6x^-1/3

Should I have done something with the 25 on the top of that fraction? I'm really not sure.

Thanks in advance.