I'm not sure about the specific content. I use the No.2 published by higher education, and No.1 is a general engineering science, and the number is lower. It's more difficult, mainly because the content is a little too much. Students who listen to the number one say that they don't have to focus on solving differential equations with constant coefficients, but I have to master the number two. In short, those who are partial to engineering should learn the number one, and those who are partial to theory should learn the numbers two and three.