calculus
posted by isha .
find derivative of (8sqrt(x)+(9/2root3(x)))^2

You have not supplied sufficient parentheses to render the expression unambiguous, that probably explains why you get different results from different sources.
Is it
(9/2)root3(x)
or
9/(2root3(x)) ? 
its like 9/2(x)^1/3

It is still not clear to me if (x)^1/3 is with the numerator or the denominator.
I assume you are transcribing from a typeset fraction where the paretheses around the denominator are understood. When transcribing to a single line (as in this case), you will need to insert explicitely the parentheses around ALL denominators and numerators to avoid ambiguity. 
its in denominator

So we're looking at find the derivative of the following expression:
y=(8*sqrt(x)+((9/2)/(x)^(1/3)))^2
Using the chain rule, we get
dy/dx
= 2(8*sqrt(x)+((9/2)/(x)^(1/3))) * d(8*sqrt(x)+((9/2)/(x)^(1/3)))/dx
By writing
=(8*sqrt(x)+((9/2)/(x)^(1/3)))^2
=8x^(1/2) + (9/2)x^(1/3)
We can differentiate u using the power rule:
du/dx = 8(1/2)x^(1/2) + (9/2)(1/3)x^(4/3)
So dy/dx
=2(8*sqrt(x)+((9/2)/(x)^(1/3)))*(8(1/2)x^(1/2) + (9/2)(1/3)x^(4/3) )
=64+12x^(5/6)(27/2)x^(5/3)
after simplification.
Check my work. 
is this the final answer?

Yes it is, but you should check my work to make sure you understand how this is done, and that I did not make a mistake.