2n+1的平方-2n-1的平方因式分解懂得来

(2n+1)²-(2n-1)²
=[(2n+1)+(2n-1)][(2n+1)-(2n-1)]
=(2n+1+2n-1)(2n+1-2n+1)
=4n×2
=8n
999²-998²
=(999+998)(999-998)
=999+998
=1997