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In mathematics, a negative number is a real number that is less than zero. Negative numbers represent opposites. If positive represents movement to the right, negative represents movement to the left. If positive represents above sea level, then negative represents below level. If positive represents a deposit, negative represents a withdrawal. They are often used to represent the magnitude of a loss or deficiency. A debt that is owed may be thought of as a negative asset, a decrease in some quantity may be thought of as a negative increase. If a quantity may have either of two opposite senses, then one may choose to distinguish between those senses—perhaps arbitrarily—as ''positive'' and ''negative''. In the medical context of fighting a tumor, an expansion could be thought of as a negative shrinkage. Negative numbers are used to describe values on a scale that goes below zero, such as the Celsius and Fahrenheit scales for temperature. The laws of arithmetic for negative numbers ensure that the common sense idea of an opposite is reflected in arithmetic. For example, − − 3 = 3 because the opposite of an opposite is the original thing. Negative numbers are usually written with a minus sign in front. For example, −3 represents a negative quantity with a magnitude of three, and is pronounced "minus three" or "negative three". To help tell the difference between a subtraction operation and a negative number, occasionally the negative sign is placed slightly higher than the minus sign (as a superscript). Conversely, a number that is greater than zero is called ''positive''; zero is usually〔For exceptions, see signed zero.〕 thought of as neither positive nor negative.〔The convention that zero is neither positive nor negative is not universal. For example, in the French convention, zero is considered to be ''both'' positive and negative. The French words positif and négatif mean the same as English "positive or zero" and "negative or zero" respectively.〕 The positivity of a number may be emphasized by placing a plus sign before it, e.g. . In general, the negativity or positivity of a number is referred to as its sign. Every real number other than zero is either positive or negative. The positive whole numbers are referred to as natural numbers, while the positive and negative whole numbers (together with zero) are referred to as integers. In bookkeeping, amounts owed are often represented by red numbers, or a number in parentheses, as an alternative notation to represent negative numbers. Negative numbers appeared for the first time in history in the ''Nine Chapters on the Mathematical Art'', which in its present form dates from the period of the Chinese Han Dynasty (202 BC – AD 220), but may well contain much older material.〔Struik, page 32–33. "''In these matrices we find negative numbers, which appear here for the first time in history.''"〕 Liu Hui (c. 3rd century) established rules for adding and subtracting negative numbers.〔 By the 7th century, Indian mathematicians such as Brahmagupta were describing the use of negative numbers. Islamic mathematicians further developed the rules of subtracting and multiplying negative numbers and solved problems with negative coefficients.〔 Western mathematicians accepted the idea of negative numbers by the 17th century. Prior to the concept of negative numbers, mathematicians such as Diophantus considered negative solutions to problems "false" and equations requiring negative solutions were described as absurd.〔Diophantus, ''Arithmetica''.〕 ==Introduction== 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「negative number」の詳細全文を読む スポンサード リンク
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