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Comments in green were written by me. Comments in blue were not written by me.

Interesting tautologies

PhD thesis, chapter 5

PhD thesis, chapter 4

PhD thesis, chapter 3

Inverting a matrix

PhD thesis, chapter 2

Gaussian elimination

Matrix multiplication

Christmas (2019) is over

2019-12-171. How many numbers between 1 and 10,000 have 1 as their final digit? How many have 1 as their penultimate digit?

6. How many ways can you write 1? 2? 3? 4? 5? What's the pattern?

8. How many zeros does 10! end in? How many zeros does 20! end in? How many zeros does 30! end in?

9. Carol’s sum is odd. What does this tell you about the 5- and 6-digit numbers?

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