Optimisation Grade 12: Maximum Surface Area Cylinder

Optimisation Grade 12: Maximum Surface Area Cylinder

[roseendley]

Hi Kevin, Why do we plug the negative 2 exponent back into the first derivative after it's been cancelled?

[nomenalstyles]

Thanks broo took your advice and decided to study the formulas only took 15 mins⛳🏌️‍♀️. Do you have videos on Rates of Change?

[dovahpass]

This gives the minimum surface area, not the maximum.

[nicolac.]

hey umm... this is wrong. Like blatantly wrong. This does not give the maximum area, it gives the minimum area. If you plot the graph of A = 2πr^2 + 40/r (only for r > 0 cause it's a length), you will see that, very clearly, the function has only one turning point: from a negative slope to a positive one. Ergo, the function has a minimum value.