Why is (n-1)(n+1)=n^2-1?
Last Updated: 19.06.2025 03:03
n^2 - n + n - 1
The basic answer is that you cross-multiply the values in each factor:
n^2 - 1
xxx
xxx x
xxx
xx
Move the nub up to the top:
(n - 1)(n + 1)
How far back into your childhood can your remember and what is your favorite memory of that time?
So, that’s a rectangle with sides 2 and 4.
xxxx
xxx x
xxxx
If you cut off the end of that rectangle, you make it smaller, 2 * 3 and a separate nub of size 1 * 2
The more direct answer is to look at a rectangle with sides of n + 1 and n - 1, let’s go with n = 2
How do you handle your mother-in-law after you heard her talking badly about you in the next room?
And you are left with almost a square. One less than the square of side n.