I have started reviewing derivative in class and have a few questions.

First off I am wondering if I have calculated the derivatives for the following correctly.

1) f(t) = 2 - (2/3)t

f'(t) = -2/3

2)f(x) = (√x^5)- 3x^-7

f'(t) = (√5x^4) - 21x^-8

My second question is there is a derivative rule for the sum which states "The derivative of a sum is the sum of the derivatives".

Is there a rule that applies the same way for the difference? Which would state the derivative of a difference is the difference of the derivatives?

Thanks for any help