9-1 = 8 * 1 25-9 = 8 * 2 49-25 = 8 * 3 81-49 = 8 * 4, what rule do you find by observing the above formula? Express this rule with formula (letter)

9—1=8*1 =3^2-1^2
25—9=8*2 =5^2-3^2
49—25=8*3 =7^2-5^2
81—49=8*4,=9^2-7^2
So it's all the square difference of adjacent odd numbers, and the result is a multiple of 8
So (2n + 1) ^ 2 - (2n-1) ^ 2 = 8N

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