Why is (n-1)(n+1)=n^2-1?
13.06.2025 06:55
xxxx
xxx x
xxx x
xx
(n - 1)(n + 1)
The basic answer is that you cross-multiply the values in each factor:
How do I explain to my husband that my 19-year-old son has accidentally gotten me pregnant?
n^2 - 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
xxxx
Why is my ex still keeping in touch with me even though she dumped me?
n^2 - n + n - 1
If you cut off the end of that rectangle, you make it smaller, 2 * 3 and a separate nub of size 1 * 2
And you are left with almost a square. One less than the square of side n.
Move the nub up to the top:
xxx
xxx
So, that’s a rectangle with sides 2 and 4.