The teacher said to find out the numbers first? Then find this symbol. The teacher means to ignore the symbols first. For example, the odd power of (-1) is-1, and the even power of (-1) is 1. Another example is (-1)*(n+ 1) and so on. No matter what number is multiplied after (-1), the final result only changes the parity of this number.

(n+ 1) When n is odd, then n+ 1 becomes even. When n is even, then n+ 1 becomes odd.

(2n+ 1) and (2n- 1) No matter what number n is, 2n+ 1 is an odd number.

(- 1)n？ When n is odd, the result is odd. When n is even, the result is even.

Expanding thinking: 3n is the same as N, as analyzed above. 4n is like 2n(4n=2*2n=2(2n)) and so on.

The result of this topic is: (-1)n When n is odd, the final result is odd, that is,-n. When n is even, the final result is even, that is, n.

Thank you ~ ~ ~