Sign more or less

The sign more or less (±) is a mathematical symbol usually used to indicate a Précision, in a Approximation, or like short cut in the notation of a quantity with two possible values.

This last use for example is met in the formula of the solutions of the quadratic equation:

if $ax^2 + bx + C = 0$ and $b^2 - 4ac > 0$ , then:

X = \ frac {- B \ pm \ sqrt {b^2-4ac \}} {2a} In other words, the two solutions of the equation are:

X = \ frac {- B + \ sqrt {b^2-4ac \}} {2a} and

X = \ frac {- B - \ sqrt {b^2-4ac \}} {2a} by using the sign ±, these two expressions are contracted in a single formula.

The use of the sign ± for an approximation in is close. For example, “5 ± 0,2” indicates a quantity which is with less than 0,2 unit of 5; i.e. between 5 - 0,2 and 5 + 0,2, therefore between 4,8 and 5,2. This approximation can also note 5.

In Unicode, the sign more or less has as a code U+00B1, and its representation HTML is & plusmn; .

There is also a character minus sign or more (∓); its code is U+2213. This symbol is seldom seen; it can be used accompanied by “±” in expressions like “X ± there ∓ Z”, which can be interpreted like “X + there - Z” or “X - there + Z”, but not “X + there + Z” or “X - there - Z”. Symbols top being apairés, in the same way for the symbols of bottom, even in the absence of a visual indication of the dependence. The initial expression can be rewritten “X ± (there - Z)”, to avoid any confusion.

This sign should not be confused with the Kanji (ground) and (the warrior)

See too

Plus signs and less
Sign of equality
Table of the mathematical symbols

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