Differential and Integral Calculus (21-120) — Feedback on Homework 9

Homework 9 was due on Thursday 24th October 2013 and consisted of:

I marked 4.5/42 (out of 4) and 4.7/14 (out of 4); two free marks were given for submitting the homework.

Section 4.5 Q42. I graded this problem very leniently; provided you'd found the derivatives correctly and identified the correct root, local maximum, infinite behaviour and inflection point, you got all the marks. Graphs could have been better labelled, though!

Section 4.7 Q14. This was done well by almost everyone. The most common error was failing to check that the obtained value is a minimum rather than a maximum value. Another common error was using the wrong formula for the surface area of an open box: many people solved the problem for a closed box!

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