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In elementary mathematics, the additive inverse is often referred to as the opposite number, [3] [4] or its negative. [5] The unary operation of arithmetic negation [6] is closely related to subtraction [7] and is important in solving algebraic equations. [8] Not all sets where addition is defined have an additive inverse, such as the natural ...
Since 2 × (−3) = −6, the product (−2) × (−3) must equal 6. These rules lead to another (equivalent) rule—the sign of any product a × b depends on the sign of a as follows: if a is positive, then the sign of a × b is the same as the sign of b, and; if a is negative, then the sign of a × b is the opposite of the sign of b.
The plus sign (+) is a binary operator that indicates addition, as in 2 + 3 = 5. It can also serve as a unary operator that leaves its operand unchanged (+x means the same as x). This notation may be used when it is desired to emphasize the positiveness of a number, especially in contrast with the negative numbers (+5 versus −5).
Any two consecutive integers have opposite parity. A number (i.e., integer) expressed in the decimal numeral system is even or odd according to whether its last digit is even or odd. That is, if the last digit is 1, 3, 5, 7, or 9, then it is odd; otherwise it is even—as the last digit of any even number is 0, 2, 4, 6, or 8.
2. Denotes the additive inverse and is read as minus, the negative of, or the opposite of; for example, –2. 3. Also used in place of \ for denoting the set-theoretic complement; see \ in § Set theory. × (multiplication sign) 1. In elementary arithmetic, denotes multiplication, and is read as times; for example, 3 × 2. 2.
An early occurrence of proof by contradiction can be found in Euclid's Elements, Book 1, Proposition 6: [7] If in a triangle two angles equal one another, then the sides opposite the equal angles also equal one another. The proof proceeds by assuming that the opposite sides are not equal, and derives a contradiction.
There are 4 different non-self-opposite rings out of the total number of 50 rings with unity [7] having 16 elements (37 [8] commutative and 13 [5] noncommutative). [6] They can be coupled in two pairs of rings opposite to each other in a pair, and necessarily with the same additive group, since an antiisomorphism of rings is an isomorphism of ...
For example, 10 is a multiple of 5 because 5 × 2 = 10, so 10 is divisible by 5 and 2. Because 10 is the smallest positive integer that is divisible by both 5 and 2, it is the least common multiple of 5 and 2. By the same principle, 10 is the least common multiple of −5 and −2 as well.