(x-2y)³·(2y-x)的2n-1次方÷(x-2y)的2n+2次方
=-(x-2y)³·(x-2y)的2n-1次方÷(x-2y)的2n+2次方
=-(x-2y)²(x-2y)³·(2y-x)的2n+1次方÷(x-2y)的2n+2次方(x-2y)³·(2y-x)的2n+1次方÷(x-2y)的2n+2次方=-(x-2y)³·(x-2y)的2n+1次方÷(x-2y)的2n+2次方=-(x-2y)的4次方