As soon as the variable intervenes in x, y, z, t, or whatever, you have to consider it as a function, not like a variable, so you're likely to use the product, quotient or chain rule =)
Next I need help with the chain rule. I understand how to do this, but I am having problems with one question. The question is:
Sqrt (2x)/(x^2+1.8)) <- For this problem, everything is under the radical.
The chain rule says that the derivative is
So calculate with the quotient rule.
Always do things step by step. It's pretty tricky for someone who is not used to differentiating to do it without taking u(x).