Second, the repeated study in senior grades has broadened my knowledge.

So, looking back, the problem that was difficult before is very simple.

For example, a difficult application problem is only difficult in elementary school arithmetic, but after algebra in junior high school, it can be solved by column equation method, which is much simpler than arithmetic!

On the contrary, it is more interesting to solve the application problem of binary or ternary linear equations in junior high school with elementary school arithmetic.

Similarly, some application problems of conditional extremum in advanced mathematics can be solved by Lagrange multiplier method without format calculation, but it is more interesting for me to solve porridge with elementary mathematical methods (such as discriminant method, triangular method of substitution method, inequality method, vector method, etc.). I always think that elementary mathematics is much more skillful and flexible than advanced mathematics!