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

12.06.2025 14:10

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

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

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How old is planet Earth? Is it 4.5 billion years old or 6,000 years old?

(n - 1)(n + 1)

n^2 - 1

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n^2 - n + n - 1

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

Is Jesus God almighty?

Move the nub up to the top:

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

Why is there no great temptress figure in any of Tolkien’s major works?

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