Can anyone tell me how to workout this problems, with the answers? I'd really appreciate it.

#3) Find the derivative of the function

y = 6 / x^2 - 3 / x

dy / dx = ?

#4) Find derivative of function

y = -9 / [2nd root SQRT(x)]

#6) Find the slope and equation of the tangent line at the given x value:

f(x) = x^4 - 2x^2 + 1 where x = -2

If you could please work these out I would really appreciate it. Thanks all!