I have three questions from my calculus homework that have confused me..

First.. I've been trying to evaluate this limit but it keeps messing me up.

Second, this confused me, also..

Let f(x) = . Is the function f(x) continuous at x = 0? Can the function be extended to that it is continuous?

Lastly..this one is just worded oddly..

Show that the line y = mx + b is its own tangent at any point

().

If any one could help me on any\all of this, I'd be very grateful ^_^ By the way, we haven't learned real derivatives yet so we have to do everything the long way in our work..