need answers to these 4 questions soon!!

1. If the graph of f(x)=2x^2+k/x has a point of inflection at x=-1, what is the value of k?

2. If f(x)=3x^2-8x^-2, then lim f(2+h)-f(2)/h =?

h->0

3. For what values of x is the graph of y=2/(4-x) concave downward?

4. If the graph of f(x)=Ax^2+Bx+C where A,B, and C are constants, passes through the point (-1,-15) and attains a relative maximum at the point (2,3), then what are the values of A,B, and C?

I need to know that answers ASAP because i have a final next week and i need to know this. thanks a lot.