Identities

a^2+b^2

can have the following 2 presentations

1. It is not an algebraic identity.

2.

a^2+b^2
= a^2+2ab+b^2-2ab
= (a+b)^2 - 2ab

a² + b² = (a + b)² - 2ab

附註：
a² - b² = (a + b)(a - b)

a³ + b³ = (a + b)(a² - ab + b²)
a³ - b³ = (a - b)(a² + ab + b²)

n-1n-2n-2n-1
aⁿ - bⁿ = (a - b)(a+ ab + ... + ab+ b), for all n is odd