Natural number: When we count objects, 1, 2, 3, ... are called natural numbers. There is no object, which is represented by 0. 0 is also a natural number. Natural numbers are all integers. Fraction: divide the unit "1" into several parts on average, and the number representing such one or several parts is called a fraction. The number representing one of them is the decimal unit of this fraction. When two integers are divided, their quotient can be expressed as a fraction. That is: a ÷ b = a/b (b ≠ 0) Decimal: Divide the integer "1" into 10, 100, 1000, ... such one or more parts are tens or hundreds. For example, 0. 1 is a decimal. Finite decimal: the decimal part of a decimal has a limited number of digits, which is called a finite decimal. Cyclic decimal: a decimal, starting from a certain bit of the decimal part, and one or several numbers are repeated in turn. Such decimals are called cyclic decimals. Cyclic decimal is infinite decimal. The greatest common divisor: the divisor of several numbers is called the greatest common divisor of these numbers, and the greatest is called the greatest common divisor of these numbers. Prime number: concept: the common divisor has only 1 two numbers. (1), some coprime (1), 1 and any natural number; ② Two adjacent natural numbers; Prime number ③, two different prime numbers) ②, not necessarily prime numbers (①, a prime number and a composite number; 2, two different composite numbers) Prime number: A number is called a prime number if it only has 1 and its two divisors. Sum number: a number. If there are other divisors besides 1 and itself, it is called a composite number. ★ The divisor of a number is finite, in which the smallest divisor is 1 and the largest divisor is itself; The number of multiples of a number is infinite, and the smallest multiple is itself. The minimum multiple of a number is equal to its maximum divisor. Rational number, positive integer 0 negative integer collectively referred to as integer. Positive and negative scores are collectively called scores. Integers and fractions are collectively called rational numbers, irrational numbers, infinitely circulating decimals are collectively called irrational numbers, rational numbers and irrational numbers are collectively called real numbers, imaginary numbers and negative numbers, and there is no solution within the range of real numbers. Mathematicians call the result of this operation an imaginary number, because such an operation cannot be explained in the real number range, so it is called an imaginary number. A pair of numbers consisting of complex numbers, real numbers and imaginary numbers is regarded as a number within the range of complex numbers, so it is called complex numbers. Thus, the real number becomes a special complex number (lacking ordinal number), and the imaginary number also becomes a special complex number (lacking real number). Function, function is that there are two variables X and Y in a certain change process, and the variable Y changes with the variable X and depends on X. If the variable X takes a specific value and Y takes a corresponding value according to a certain relationship, then it is said that Y is a function of X. Transcendental number cannot satisfy the real number of any algebraic equation with integral coefficients. E and π are transcendental numbers. . . . .

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