A (2 k)-b (2 k) = (a 2) k-(b 2) k = factorial: (a 2-b 2) = (a-b) (a+b).
For example: (a+b) 4 = a 4+4a 3b+6a 2b 2+4ab 3+b 4.
(a+b)^5=a^5+5a^4b+ 10a^3b^2+ 10a^2b^3+5ab^4+b^5。
The most basic definition of power is:
Let a be an arbitrary number, n be a positive integer, and the n power of a be expressed as a? That represents the result of n times multiplication, such as 2? =2×2×2×2= 16。 The definition of power can also be extended to zero power, negative power, fractional power, irrational power and even imaginary power. When inputting mathematical formulas on the computer, because it is inconvenient to input the power, the symbol ""is often used to represent the power. For example, the fifth power of 2 is usually expressed as 2 5.