Can anyone differentiate these problems with ti-89?

Hi there

I can't really get these problems right(Worried)

Here is:
f(x)= 3x(root(x)-x^5)/root(x)
and
Y=-2/root(4-x)
and also
Y= 1/x^2+5
with this one i get -1/4 but the answer is not negative it's 1/4(Worried)
Thanks guys(Happy)