We looked some at the previous test. But focused on material for the upcoming test.
One thing was the product rule, he had made a mistake before with it on another test.
Often there were small algebraic errors. The new material seems fairly comfortable though.
If you make a mistake early on it can continue to be in your work for the entirety of the problem and depending on the direction of where you go with the problem, it can get bigger. Let’s say you have four instead of two, then you square that number, suddenly the mistake got larger.
Calculus involves a lot of algebra, geometry, etc. Sometimes there can be many steps and mistakes add up and get bigger. Often times it is better to slow down a bit and be careful rather than hunt for mistakes later on.