(y-2x)^3 乘 (2x-y)^2n+1除以(y-2x)^2n+3

(y-2x)^3*(2x-y)^(2n+1)/(y-2x)^(2n+3)
因为2n+1是奇数
所以(2x-y)^(2n+1)=-(y-2x)^(2n+1)
所以(y-2x)^3*(2x-y)^(2n+1)/(y-2x)^(2n+3)
=-(y-2x)^3*(y-2x)^(2n+1)/(y-2x)^(2n+3)
=-(y-2x)^[3+2n+1-(2n+3)]
=-(y-2x)^1
=2x-y

(y-2x)³ (2x-y)^(2n+1)/(y-2x)^2n+3
=(2x-y)^(2n+1)/(y-2x)^2n
=(2x-y)((2x-y)/(y-2x))^2n
=(2x-y)(-1)^2n
=2x-y

要简便先把第三个与第二个的顺序换下
得到(y-2x)^3÷(y-2x)^2n+3×(2x-y)^2n+1
等于(y-2x)^-2n×(2x-y)^2n+1
等于y-2x