Why is (n-1)(n+1)=n^2-1?
Last Updated: 23.06.2025 12:38

xxx
(n - 1)(n + 1)
xxxx
MIT Breakthrough: Star-Shaped Brain Cells Could Be the Secret Behind Human Memory - SciTechDaily
The more direct answer is to look at a rectangle with sides of n + 1 and n - 1, let’s go with n = 2
So, that’s a rectangle with sides 2 and 4.
n^2 - n + n - 1
New Videos Show How Fantasy Life i Has Been Beefed Up On Switch 2 - Nintendo Life
And you are left with almost a square. One less than the square of side n.
xxx x
xx
Light Squeezed Out of Darkness in Surprising Quantum Simulation - ScienceAlert
n^2 - 1
Move the nub up to the top:
xxx
If you cut off the end of that rectangle, you make it smaller, 2 * 3 and a separate nub of size 1 * 2
The basic answer is that you cross-multiply the values in each factor:
xxxx
xxx x