9一1=8,16一4=12,25—9=16,36-16＝20,用n表示自然数用关于n的等式表示出来

9-1 = 3² - 1² = (1 + 2)² - 1² = (3 + 1)(3 - 1) = 4*2 = 8 = 4*(1 + 0)
16 - 4 = (2 + 2)² - 2² = (4 + 2)(4 - 2) = 6*2 = 12 = 4*(2 + 1)
...
(n + 2)² - n² = (n + 2 + n)(n + 2 - n) = 4(n + 1)

其规律为：n²-(n-2)²=4*(n-1)