原式=[(4x的n+1次方)²-2×4x的n+1次方×(1/2y)+(1/2y)²+4x的n次方y-1/4y²]÷8x²
=(16x的2n+2次方-4x的n+1次方y+1/4y²+4x的n次方y-1/4y²)÷8x²
=(16x的2n+2次方-4x的n+1次方y+4x的n次方y)÷8x²
=16x的2n+2次方÷8x²-4x的n+1次方y÷8x²+4x的n次方y÷8x²
=(16÷8)×(x的2n+2次方÷x²)-(4÷8)×(x的n+1次方÷x²)×y+(4÷8)×(x的n次方÷x²)×y
=2x的2n次方-1/2x的n-1次方y+1/2x的n-2次方y