This week's updated lecture note uploaded and re-uploaded

... yes, reuploaded 19:28, so if you managed to get it before that: please reload.

There are some changes to relative to the Wed@1AM version, and the first of them will be elaborated after the list:

• The "find an expression for" clarification on slide 18 likely asks for too much in certain cases (though not the example given that page). Good news: "less to do". Bad news: further clarification needed.
  See brief explanation given below - and examples next week.
• New: 31 and 32 have calculations from Wednesday's class
• Bugfixes: fixed numbers in last line p30, misleading wording about what the cofactor is (last line p27), added the word "inverses" in 2nd bullet item p22 due to question in class. 
• Slides 9, 16, 23, 24 now clearer about what was less stressed in class. (That reflects priority.)
• Some Tue-to-Wed changes no longer indicated. Some of the above-mentioned slides tweaked to get space for the changes. 

On to that "clarification". Example: the good old marginal rate of substitution is commonly written as the ratio between derivatives. That is a good enough "expression for the MRS" - even if it could actually happen that we have functions where both those derivatives are zero, at a point where the isoquant/indifference curve still has a well-defined slope. 
A "find an expression for the MRS" question would not ask you to make any "except when ... when it is ...". 

We will see exam-relevant examples next week, so right now I won't elaborate further.