Hello there!

can you me with this calculus homework? well i did some of it, but i am stuck with #4, 8 and 10. just these three!
don't forget to show your work or : )
and happy valentine's day!

4. dy/dx = -2

8. dy/dx = 1/2 x^(-3/2)

10/ dy/dr = 4 pi r^2

Step-by-step explanation:

4.  y = -2x+7

dy/dx = -2(1)

dy/dx = -2

8.  y = 4 - x^-1/2

 dy/dx =  - (-1/2x^ (-1/2-1)

 dy/dx = 1/2 x^(-3/2)

10.  y = 4/3 pi r^3

dy/dr = 4/3 pi  (3r^2)

dy/dr = 4 pi r^2