This formula can simplify the calculation directly, and (a-b)? Decomposition is a multiplication of square difference and a subtraction.

(a-b)? =(a-b)？ (A-B)

Finally =a? -3a？ b+3ab？ -B?

Extended data

The complete cubic difference formula is a mathematical formula, namely (a-b)? =a？ -3a？ b+3ab？ -B?

Cubic sum formula

Difference of cube

Three-term cubic sum formula

Complete cubic formula

edit

(a-b)? =a？ +3ab？ -3a？ b-b？

The decomposition steps are as follows

(a+b)3 =(a+b)(a+b)(a+b)=(a2+2ab+B2)(a+b)= a3+3a2b+3ab 2+B3

It is often used to solve problems:

(a+b)3= a3+ b3+ 3ab(a+b) and a3+ b3= (a+b)3- 3ab(a+b)

(a-b)? =(a-b)(a-b)(a-b)=(a？ -2ab+b？ )(a-b)=a？ -3a？ b+3ab？ -B?

Cubic sum accumulation

Within a positive integer range

Note: It can be proved by mathematical induction.

Refer to Baidu Encyclopedia-Complete Cubic Difference Formula