1. At what point on the graph of f(x)=(x-8)(x-2)/x-4 would you not be able to determine the instantaneous rate

Question

of change? Explain.

Answer 1

Assuming you meant
f(x)=(x-8)(x-2)/(x-4)
the function is undefined when x = 4 , (we would be dividing by zero)
thus the derivative (the instantaneous rate of change) at x = 4 does not exist

if your meant it the way you typed it, then the above happens at x = 0