Show that n square -1 is …

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Ram Kushwah 6 years, 9 months ago
The question is like this:
Show that n2 - 1 is divisible by 8, if n is an odd positive integer
Soln:Any odd positive integer n can be written in form of 4q + 1 or 4q + 3.
If n = 4q + 1, then
n2 - 1 = (4q + 1)2 - 1 = 16q2 + 8q + 1 - 1 = 8q(2q + 1) which is divisible by 8.
If n = 4q + 3,then
n2 - 1 = (4q + 3)2 - 1 = 16q2 + 24q + 9 - 1 = 8(2q2 + 3q + 1) which is divisible by 8.
So, n2 - 1 is divisible by 8, if n is an odd positive integer.
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