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Why is (n-1)(n+1)=n^2-1?

Last Updated: 18.06.2025 05:06

Why is (n-1)(n+1)=n^2-1?

(n - 1)(n + 1)

The more direct answer is to look at a rectangle with sides of n + 1 and n - 1, let’s go with n = 2

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— we are metamorphosing!

n^2 - 1

If you cut off the end of that rectangle, you make it smaller, 2 * 3 and a separate nub of size 1 * 2

Move the nub up to the top:

It seems that I am cursed with bad luck. How do I break such a curse?

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The basic answer is that you cross-multiply the values in each factor:

And you are left with almost a square. One less than the square of side n.

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So, that’s a rectangle with sides 2 and 4.

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Have you ever had a scary dream about a loved one or friend soon after their death?

n^2 - n + n - 1