1. ## Derivatives and first principles ??? help please

What is the difference between deriving and deriving using first principles ?

for example how would you use first principles to find the derivative of y=7/(rootx + 6)

and y = 1 / 2x

2. Originally Posted by nosh
What is the difference between deriving and deriving using first principles ?

for example how would you use first principles to find the derivative of y=7/(rootx + 6)

and y = 1 / 2x
Finding derivatives by first principles means to use the definition of the derivative. recall that we define the derivative of a function $f(x)$ as follows

$f'(x) = \lim_{h \to 0} \frac {f(x + h) - f(x)}h$

provided the limit exists.

now use that to find the derivatives. you can check your answers by doing the derivatives the short way