Use the limit definition of the derivative to find f′(x) if

Question

1. f(x) = x^2 + 3x
2. f(x) = 1/x + 1

now what i am confuse with is that there is no value given for x. So how is one suppose to do these problems. please show steps and this is just the 3rd chapter of my calc book so don't use shortcuts that come in the future.

Answer 1

this will help you:

tutorial(dot)math(dot)lamar(dot)edu/Classes/CalcI/DefnOfDerivative.aspx

Answer 2

are you using the defn. of
LIm (f(x+h) - f(x)/h, as h ---> 0 ?