The formula can be applied not only from left to right (multiplication expansion), but also from right to left (factorization). Remember some important formula variants and their inverse operations, such as division.
2. The basic formula is the most commonly used and basic formula, from which other formulas can be derived.
Complete square formula: (A B) 2 = A2AB+B2
Square difference formula: (a+b)(a-b)=a2-b2,
Cubic sum (difference) formula: (a b) (a2mab+B2) = a3 B3.
meaning
3×5 means the addition of five 3s.
5x3 represents the addition of three 5s.
Another: the new meaning of multiplication: multiplication is not a simple notation of addition.
If there is a direct ratio between the dependent variable f and the independent variable X 1, X2, X3, ... Xn are qualitatively different from each independent variable, without any independent variable f, it will lose its meaning, which is called multiplication.
In probability theory, the result of an event needs to be divided into n steps, the first step 1 includes M 1 different results, the second step includes M2 different results, …, and the n step includes Mn different results. Then this event may have n = m 1× m2× m3×…× Mn different results.