rewrite key points from lecture notes

• [x] lecture 9
• [ ] lecture 10
• [ ] lecture 11
• [ ] lecture 12
• [ ] lecture 13
• [ ] lecture 14

first 10 hw 5 questions

• [x] 14.3:22
• [x] 14.3:44
• [x] 14.3:48
• [x] 14.3:52
• [x] 14.3:60
• [x] 14.4:4
• [x] 14.4:12
• [x] 14.4:26
• [x] 14.4:36
• [x] 14.4:46

practice midterm

• [ ] attempt practice midterm