Have to find derivatives of following problems:

For this one, I simplified to :

(-4x^5 * x^(1/2)) + ((-7)/(x^3 * x^1/2))

-4^(11/2) + -7x^(-7/2)

Ended with:

-22x^(9/2) + (-49/2*x^(-9/2))

Is there something I'm doing wrong?

For this one I tried making it :

5^(1/2) * t^-3

-15^-3/2 * t^-4

ended with 1/(15^(3/2) * t^4)

Is that correct?

I ended with 4/(x^(1/2))

Correct?

For this one, how would I do about solving this with the x on the bottom also?

Lastly:

How do you find the derivative at that point?

I got -6x-3 for the line, but what do i do after that?