(a-b)^(2n-1)+(b-a)^(2n+1)
=(a-b)^(2n-1)-(a-b)^(2n+1)
=(a-b)^(2n-1)×[1-(a-b)²]
=(a-b)^(2n-1)×(1-a+b)×(1+a-b)