Scientist Li Siguang has a famous saying: "You cannot see the truth without doubting". This sentence is quite profound. Generally speaking, bold opinions and scientific explanations of doubts are often connected together. Questions are raised amid doubts and will inevitably be solved through in-depth research. The solution of the problem is the beginning of obtaining true knowledge and insights. The reason why the mathematician Hua Luogeng was able to achieve outstanding results one after another in the field of mathematics was precisely because he could boldly identify doubts and scientifically answer doubts based on ready-made formulas, theorems and conclusions in books. His first step towards climbing the peak of mathematics began here.