Given the function f(x)=x2−2x, which of the following is the correct limit definition of f′(2)?
a) limh→0f(2+h)−f(2)/h
b) limh→0f(2)−f(2−h)/h
c) limh→0f(2+h)−f(2−h)/2h
d) limh→0f(2−h)−f(2)/h