Hi all,

I've gotten somewhere on two of these, but I'm stuck on all three

1) If a stone is thrown vertically upward from the surface of the moon with a velocity of 6 m/s, its height (in meters) after

*t* seconds is

*h* = 6

*t* - 0.83

*t*^2. (Round the answers to two decimal places.)

Part 1: What is the velocity of the stone after 3 s?

I did this, I differentiated and solved.

Part 2 has me confused, though.

(b) What is the velocity of the stone after it has risen 8 m?

Plugging 8 in for h and solving seems like a really messy solution. Am I mistaken here?

2) When blood flows along a blood vessel, the flux

*F* (the volume of blood per unit time that flows past a given point) is proportional to the fourth power of the radius

*R* of the blood vessel.

*F* =

*kR*^4

How will a 1% increase in the radius affect the flow of blood?

I substituted some values into the function above and got ~10 but I'm assuming that was incorrect. Do I need to derive it and then take the change in R into F'?

3) y = (2ln(x))/x

Find the tangent line at (1,0) and (exp,2/exp)

I know that I need to differentiate to get the tangent line and then solve for the slope and plug it into point slope equation, but I keep getting the wrong derivative on that one, so any help would be nice.

Thanks!