Question

The cost (in dollars) of producing x units of a certain commodity is C(x)=5000+10x+0.05x^2. Find the instantaneous rate of change of C with respect to x when x=100

Answer 1

I know the formula for instantaneous rate is \[\lim _{x _{2} \rightarrow x _{1}} \frac{ f(x _{2})-f(x _{1}) }{ x _{2}-x _{1} }\] I just don't understand what to plug in where