Question

find the derivative of f(x) = |x|

Answer 1

f(x) = x when x>0
-x when x<0

f'(x) = 1 when x>0
-1 when x<0

So f'(x) = sign(x)

Answer 2

but what's the derivative?

Answer 3

What I said above. Derivative of f(x) equals sign(x).

Answer 4

how would you show that using the f(x+h)-f(x)/h equation

Answer 5

Are you asked specifically to do it that way ?

Answer 6

yea

Answer 7

Sorry couldn't get it with that method, but simply deriving f you get:
f'(x) = 1 when x>0
-1 when x<0