Chapter 4 - Applications of the Derivative - 4.5 Linear Approximation and Differentials - 4.5 Exercises - Page 289: 41

\[dy = 2dx\]

$$\eqalign{ & f\left( x \right) = 2x + 1 \cr & {\text{Differentiate}} \cr & f'\left( x \right) = \frac{d}{{dx}}\left[ {2x + 1} \right] \cr & f'\left( x \right) = 2 \cr & {\text{Write in the form }}dy = f'\left( x \right)dx \cr & dy = 2dx \cr} $$