Calculus Assignment - HELP!!!

If anyone could help me with these questions, that would be really really great.

1. Determine the derivative of f(x)=(2x^2-1)/x from first principles. Use the quotient rule to verify your answer.

2. The graph of has a f(x)=(ax+b)/((x-1)(x-4)) horizontal tangent line at (2,-1). Determine the values *a* and *b*.

3. Determine lim x-->0 (3rdroot(x-8)+2)/x

4. The tangent line to the curve defined by g(x)=(x^4-2x^3+3)/(-6x) at x=-1 intersects the curce at two other points P and Q. Determine the coordinates of P and Q, algebraically. Illustrate this situation with a graph.

Anything you can add will be majorly helpful.