Simple calculation is a special kind of calculation, which makes use of the algorithm and the basic properties of numbers, thus making the calculation simple and making it easy to calculate numbers from very complicated formulas. The most commonly used method in simple calculation is multiplication and distribution law. Multiplication and division means ax(b+c)=axb+axc, where A, B and C are arbitrary real numbers.
On the contrary, axb+axc=ax(b+c) is called the inverse application of multiplication and division (also called finding common divisor), especially when A and B are complementary to each other, this method is more useful. Sometimes we will use the law of additive combination, for example, a+b+c, B and C are complementary, so we can combine B and C and multiply by A ... If the+in the above formula is replaced by X, we can simply use the law of multiplicative combination to calculate.