rates of change...easy..??

[mykg4orce1]

Ok i need some help in the following:



This is suppose to be a rates of change calculus problem. This is among the derivative chapter. I have no clue as to what to do.



And please bare with me...this is the 2nd problem.




Please if you could offer any help on this.

[Spooner]

In q1, you're presumably stuck because there's an 'r' in your last line and although you know dr/dt is 11 you don't have a value for r?

Well if you take the derivitive of the equation for r, you get
dr/dt= 8t + 3. You know that's 11, so solve for t=1.

Then put that back into the original eqn and you get r=4+3+1= 8 so put that into your last eqn and there you go.

[mykg4orce1]

hey! thanks a lot for that.... Your help led me to solve a "third" problem which iw as hesitant to post here. thanks again.