Posted by Nancy on Monday, November 8, 2010 at 11:16pm.
Express the amount of material needed to make a can as a function of the radius. In other words, find a function A(r) such that A represents the surface area (in square inches) of the cylinder and r is the radius (in inches).
my answer (not sure)
A(r) = r^2 + 2r + 29 ?

algebra  Reiny, Monday, November 8, 2010 at 11:27pm
This looks like a continuation of your last problem
Visualize taking a tin can apart.
you would have 2 circles, the top and the bottom
plus the sleeve that forms the can.
Pretend you are opening it up by cutting along the height of the can.
Would you not have a rectangle whose length is the circumference of the circle, and whose width is the height ?
So the total area would be
top + bottom + rectangle
= πr^2 + πr^2 + (2πr)h, where h is the height.
= 2πr^2 + (2πr)h
This is precisely what I used in the previous question.
You will need the height, or else be able to calculate it like in your previous question when the volume was given. 
algebra  Nancy, Monday, November 8, 2010 at 11:43pm
Thank you!!