Power Functions

Which of the following exhibit inverse variation?

A) The distance traveled as a function of speed.

speed  =  distance / time

A bigger number for the distance causes a bigger number for the speed.     not inverse

B) The total cost as a function of the number of items purchased.

As the number of items purchased goes up, the total cost goes up.     not inverse

C) The area of a circular swimming pool as a function of its radius.

A bigger radius causes a bigger area.     not inverse

D) The number of posts in a 20ft fence as a function of distance between posts.

As the distance between posts gets larger, the number of posts gets smaller.

As the distance between posts gets smaller, the number of posts gets larger.

This is an inverse relationship.

2nd question:

If you plug the equations into this calculator:

https://www.desmos.com/calculator

then you can get the answers for yourself. :)

I'll do as many of the second question as I can....some are hard to tell

y = -(2/3)x^4   appears to be  "i"

y =  (1/2)x^-5  the half-graph appears to be "a"

y = 2x^1/4    don't see one that appears to match this one

y =  - x^5/3    don't see one that appears to match this one

y = -2x^2    "j"  is the one that seems to match this one

y = 1.7x^2/3     "d"  is the one that seems to match this one