= 1+( 1/2- 1/3)+( 1/3- 1/4)+…+( 1/ 19+- 1/20)。

= 1+ 1/2- 1/3+ 1/3- 1/4+ 1/4…+ 1/ 19- 1/20。

Tips for learning mathematics

1, you should be good at thinking when learning mathematics, and the answers you come up with are far more impressive than those others say.

2. Do a good preview before class, so that we can better digest and absorb the unknown knowledge points in math class.

3, the mathematical formula must be memorized, and it must be deduced and can be deduced.

4. The most basic thing to learn mathematics well is to master the knowledge points of textbooks and exercises after class.

5. 80% of the scores in mathematics come from the basic knowledge, and 20% of the scores are difficult, so it is not difficult to test 120.