Question

if n is an odd integer show that n^2-1 is divisible by 8​

Answer 1

Answer:

Any odd positive integer n can be written in form of 4q + 1 or 4q + 3.

 

If n = 4q + 1, when n2 - 1 = (4q + 1)2 - 1 = 16q2 + 8q + 1 - 1 = 8q(2q + 1) which is divisible by 8.

If n = 4q + 3, when n2 - 1 = (4q + 3)2 - 1 = 16q2 + 24q + 9 - 1 = 8(2q2 + 3q + 1) which is divisible by 8.

 

So, it is clear that n2 - 1 is divisible by 8, if n is an odd positive integer.

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Answer 2

Step-by-step explanation:

Let n be 3,

Then,

3² - 1 = 9 - 1 = 8

8 is divisible by 8,

Now, if we take 15 as n,

15² - 1 = 225 - 1 = 224

As 224 is also divisible by 8,

n² - 1 is divisible by 8

Hope it helped!!