# Homework Help: Differentials - not understanding directions

1. Jan 10, 2010

### lp27

1. The problem statement, all variables and given/known data
Find dy and evaluate dy for the given value x and dx
.

y = x^3 - 3x, x = 2, dx = 0.05

2. Relevant equations

3. The attempt at a solution
I have no idea how to begin this problem.
I assumed that I find y'.
Then plug in x into y'.
Following that, I am not sure.

2. Jan 10, 2010

### diazona

$$\mathrm{d}y = \frac{\mathrm{d}y}{\mathrm{d}x}\mathrm{d}x = y'\,\mathrm{d}x$$

3. Jan 10, 2010

### lp27

Thank you, that was straight forward.