Why is (n-1)(n+1)=n^2-1?
13.06.2025 17:05

The more direct answer is to look at a rectangle with sides of n + 1 and n - 1, let’s go with n = 2
Move the nub up to the top:
n^2 - 1
n^2 - n + n - 1
xx
The basic answer is that you cross-multiply the values in each factor:
Should parents force their kids to go to school when they are sick?
xxxx
xxx
And you are left with almost a square. One less than the square of side n.
What are the best items to buy from a furniture shop?
So, that’s a rectangle with sides 2 and 4.
xxx x
If you cut off the end of that rectangle, you make it smaller, 2 * 3 and a separate nub of size 1 * 2
Why is Tiananmen Square censored?
(n - 1)(n + 1)
xxxx
xxx x
xxx