# Homework Help: Differentiating product

1. Jan 22, 2010

### James889

Hi,

I need to differentiate the following $$\frac{d}{dx}[e^{-2x}y]$$

Does the dx mean that the y turns into x?

I know i have to use the product rule.

2. Jan 22, 2010

### tiny-tim

Hi James889!

No, you just write "dy/dx" …

d/dx ( f(x)y) = f'(x)y + f(x)dy/dx

3. Jan 22, 2010

### James889

Hm?, what do you mean just write?

I can't think of anyone i hate more than Wilhelm Leibniz, for coming up with this stupid notation

4. Jan 22, 2010

### tiny-tim

he he, get used to it!

(it's particularly useful when you start using substitution of variables in integals)

of course, you could write " y' " instead.

5. Jan 22, 2010

### Staff: Mentor

Personally, I prefer Leibniz notation over Newton's notation as being more informative. The notation dy/dx is lots more informative than, say y' inasmuch as the Leibniz notation tells you exactly which variable with which differentiation is with respect to.