2. If the exponent is odd, you need to consider the positive and negative if switching. That is, the cubic of (y-x) = the cubic of-(x-y)

3: Like 2, it involves many negative numbers. If the exponent is odd, then the odd power of (-t) = the odd power of t.

It can be understood that negative numbers are regarded as-1× positive numbers.

(-1× odd power of positive number) = odd power of (-1) × odd power of positive number =-odd power of positive number.

This is the odd power of the key (-1) = even power of1(-1) = 1.