Addition rule: add the same sign with the same sign, and add the absolute value; The symbols with larger absolute values are added, and those with larger absolute values are subtracted from those with smaller absolute values; Add a number to zero to get the original number. Law of subtraction: subtracting a number is equal to adding the reciprocal of this number.

Countdown:

Two numbers with opposite exponential values, one of which is opposite to the other. Family regret bridge A and -a are opposite numbers, and the opposite number of 0 is 0. Here a is any number, which can be positive, negative or 0. For example, 3 and (-3) are antonyms.

Absolute value:

Absolute value is the distance from a point corresponding to a number on the exponential axis to the origin, which is represented by "||". The preceding |b-a| or |a-b| indicates the distance between the point representing A and the point representing B on the number axis. The absolute value of a number can be considered as the distance from zero. The generalization of absolute value of real number appears in various mathematical settings, such as complex number, quaternion, ordered ring, field and vector space to define absolute value.

Rational number:

Rational number is the collective name of integer (positive integer, 0, negative integer) and fraction, and it is the set of integer and fraction. Integers can also be regarded as fractions with a denominator of 1 Real numbers that are not rational numbers are called irrational numbers, that is, the fractional part of irrational numbers is infinite cyclic numbers. It is one of the important contents in the field of number and algebra.

It is widely used in real life, and it is the basis for continuing to learn real numbers, algebra, equations, inequalities, rectangular coordinate systems, functions, statistics and other mathematical contents and related disciplines. The set of rational numbers can be represented by the capital black orthographic symbol q, but q does not represent rational numbers. Rational number set and rational number are two different concepts.

The set of rational numbers is the set of all rational numbers, and rational numbers are all elements in the set of rational numbers. Absolute value is closely related to concepts such as size, distance and norm in various mathematical and physical environments.