# Homework Help: Quick question on differentiation

1. Feb 20, 2010

### g$up 1. The problem statement, all variables and given/known data Find the value of the following derivative at x=1: d/dx(2v/u) where u(1)=3, u'(1)=-4, v(1)=-2, v'(1)=5 3. The attempt at a solution Differentiating the equation: [(u)(2v') - (u')(2v)]/(u^2) plugging in the values i get 14/9 as the value. now my question arises from the derivative of 2v. Would it be just 2? or 2v' as v represents a 'complex base' (therefore using the chain rule)?? the question seems simple enough to me aswell but i just want to clarify this. thanks. 1. The problem statement, all variables and given/known data 2. Relevant equations 3. The attempt at a solution 2. Feb 20, 2010 ### tiny-tim Welcome to PF! Hi g$up! Welcome to PF!
The derivative (wrt x) of 2v is definitely 2v'.

3. Feb 20, 2010

### Staff: Mentor

To expand on what tiny-tim said, d/dv(2v) = 2, but with d/dx(2v) there's a tacit assumption that v is a function of x, so d/dx(2v) = 2dv/dx = 2v'. In this problem, both u and v are assumed to be differentiable functions of x.