Difference between revisions of "Addition"

m (Fixed "zero" leading to disambiguation page)
(Properties)
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* Identity: <math>a+0=a</math> for any complex number <math>a</math>.
 
* Identity: <math>a+0=a</math> for any complex number <math>a</math>.
 
* Inverse: The sum of a number and its [[additive inverse]], <math>a+(-a)</math>, is equal to [[Zero (constant)|zero]].
 
* Inverse: The sum of a number and its [[additive inverse]], <math>a+(-a)</math>, is equal to [[Zero (constant)|zero]].
 +
* Equality: If <math>a=b</math>, then <math>a+c=b+c</math>.
 
* If <math>a</math> is real and <math>b</math> is positive, <math>a+b>a</math>.
 
* If <math>a</math> is real and <math>b</math> is positive, <math>a+b>a</math>.
 
* The sum of a number and its [[Complex conjugate]] is a real number.
 
* The sum of a number and its [[Complex conjugate]] is a real number.

Revision as of 12:48, 8 November 2008

Addition is the mathematical operation which combines two quantities. The result of addition is called a sum.

Notation

The sum of two numbers $a$ and $b$ is denoted $a+b$, which is read "a plus b." The sum of $f(a), f(a+1), f(a+2), f(a+3), \cdots, f(b)$, where $f$ is a function, is denoted $\sum_{i=a}^bf(i)$. (See also Sigma notation)

Properties

  • Commutativity: The sum $a+b$ is equivalent to $b+a$.
  • Associativity: The sum $(a+b)+c$ is equivalent to $a+(b+c)$. This sum is usually denoted $a+b+c$.
  • Closure: If $a$ and $b$ are both elements of $\mathbb{R}$, then $a+b$ is an element of $\mathbb{R}$. This is also the case with $\mathbb{N}$, $\mathbb{Z}$, and $\mathbb{C}$.
  • Identity: $a+0=a$ for any complex number $a$.
  • Inverse: The sum of a number and its additive inverse, $a+(-a)$, is equal to zero.
  • Equality: If $a=b$, then $a+c=b+c$.
  • If $a$ is real and $b$ is positive, $a+b>a$.
  • The sum of a number and its Complex conjugate is a real number.
  • $a+(-b)=a-b$ (See also Subtraction)

See also

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