Differential and Integral Calculus (21-120) — Feedback on Homework 3

Homework 3 was due on Thursday 12th September 2013 and consisted of:

I marked 3.2/50 (out of 3), 3.4/72 (out of 3) and 3.4/84 parts (a)(b) (out of 3). Part (c) wasn't marked because it was essentially an exercise in using graphing software. Everyone got 1 free point for submitting their homework.

Section 3.2 Q50. The most common error was not using the product and quotient rules correctly. A few people said that $P'(2)=F'(2)G'(2)$, for example; but by the product rule, it's actually equal to $F'(2)G(2)+F(2)G'(2)$. Another error made by a few people was saying that all the derivatives were zero. This may have been down to confusion with the notation. When you see something like $G'(7)$, it means first differentiate $G(t)$ and then substitute $t=7$ in the derivative. If you substitute first, you end up with a constant, so you'll always get zero... this is wrong!

Section 3.4 Q72. Common errors included:

Section 3.4 Q84. Most of the errors on this problem were very small:

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