Notation

Being able to -expand- and -contract- notations is often -really hard-
for students.
This is especially painful in the calc section on sequences and
series.

- formulae, esp. factorials
``Simplify $(n+1)!/n!$.''
It's $(n+1)$. Like duh.
Or how about $2^{n+1}/2^n$. Or $3^{n+1} - 3^n$.

- summations
A similar thing is:
$\sum_{k=0}^n a_k - \sum_{k=0}^{n-1} a_k$.

People -don't expand out definitions-.
