Professor

## Linfeng Li

**Most Helpful Review**

Fall 2023 - I love Linfeng Li. He’s a super cool and funny guy. Only problems with lecture are his accent can be a bit rough to understand and he tends to copy the textbook for the most part (though he’ll try to answer any questions). The weekly homework’s tend to be pretty short, and the quizzes are extremely easy (there are three during discussion weeks 3 6 and 9). The midterms were rough for me as I made a small mistake on each one that really messed up my score. He was accommodating and gave me a few points back after I explained myself but I ended up dropping that one anyways(he can drop your lowest midterm and increase the weight of the final). The final was extremely fair and very similar to resources he provided in the weeks leading up to it. Everyone I know who prepared well did well on the final, so don’t be disheartened if the midterms are a bit rough. Live Love Lifeng

**Most Helpful Review**

Spring 2024 - The course was enjoyable overall and well organized. However, I don't think I learned as much as I could have for a few reasons: First, the class was much too computational for my taste, and felt more like a sequel to 33A than to 115A. Second, proofs often relied very heavily on unproven lemmas, where all the work lies in the proof of the lemma. We essentially skipped the proofs of most major results in this manner. For instance, our "proof" of the Spectral theorem presumed the existence of an orthonormal basis of eigenvectors, and the only work we did was finding the matrix decomposition corresponding to this basis. Despite these shortcomings, I still enjoyed the lectures as they were very clear and easy to follow. Homework and exams were also very well-made.

###### AD

**Most Helpful Review**

Winter 2024 - Get ready for lots of proofs. Math 131 is essentially all your math classes up to calculus conceptualized into an abstract concept. In other words, you learn how these ideas you've learned in your past math classes come to be (i.e limits, continuity, derivatives). This class is very tricky, requiring you to think outside the box to solve these problems rather than brutal computations. You won't be faced with as much concepts compared to other math classes but with the ideas you learn, you have to apply them to its limit. There are 9 homeworks (one dropped), two midterms and one final in this class where one midterm can be dropped. Pros: - Professor is very helpful. He'll answer any questions in a concise way, making sure students understand what he meant. He's even more helpful in office hours as he goes over homework and past exam questions. Highly recommend going to his office hours as that's how I got my homework done. - Professor is very consistent with lectures. He goes over proofs well (which is rare in the math department) and even if he doesn't have time to do a proof, he lays out the structure in a way we can understand. Cons: - Homework is tough af. Every assignment feels like one of those "think outside the box" puzzle games where you have to pull some technique only 200 iq people would think of. This is why his OFFICE HOURS are HELPFUL! - Exams are just as difficult. His practice exams give you what concepts to expect on each exam but again, you have to think outside the box for each of these questions that you can't really do much to prepare except to do many practice problems. - Grading is strict, but it could've been because our T.A was a picky grader.