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  2. Imaginary unit - Wikipedia

    en.wikipedia.org/wiki/Imaginary_unit

    Square roots of negative numbers are called imaginary because in early-modern mathematics, only what are now called real numbers, obtainable by physical measurements or basic arithmetic, were considered to be numbers at all – even negative numbers were treated with skepticism – so the square root of a negative number was previously considered undefined or nonsensical.

  3. Mental calculation - Wikipedia

    en.wikipedia.org/wiki/Mental_calculation

    This method requires memorization of the squares of the one-digit numbers 1 to 9. The square of mn, mn being a two-digit integer, can be calculated as 10 × m(mn + n) + n 2. Meaning the square of mn can be found by adding n to mn, multiplied by m, adding 0 to the end and finally adding the square of n. For example, 23 2: 23 2 = 10 × 2(23 + 3 ...

  4. Complex number - Wikipedia

    en.wikipedia.org/wiki/Complex_number

    This formula distinguishes the complex number i from any real number, since the square of any (negative or positive) real number is always a non-negative real number. With this definition of multiplication and addition, familiar rules for the arithmetic of rational or real numbers continue to hold for complex numbers.

  5. Arithmetic - Wikipedia

    en.wikipedia.org/wiki/Arithmetic

    Arithmetic systems can be distinguished based on the type of numbers they operate on. Integer arithmetic is about calculations with positive and negative integers. Rational number arithmetic involves operations on fractions of integers. Real number arithmetic is about calculations with real numbers, which include both rational and irrational ...

  6. Square (algebra) - Wikipedia

    en.wikipedia.org/wiki/Square_(algebra)

    Zero is the square of only one number, itself. For this reason, it is possible to define the square root function, which associates with a non-negative real number the non-negative number whose square is the original number. No square root can be taken of a negative number within the system of real numbers, because squares of all real numbers ...

  7. Difference of two squares - Wikipedia

    en.wikipedia.org/wiki/Difference_of_two_squares

    If two numbers (whose average is a number which is easily squared) are multiplied, the difference of two squares can be used to give you the product of the original two numbers. For example: 27 × 33 = ( 30 − 3 ) ( 30 + 3 ) {\displaystyle 27\times 33=(30-3)(30+3)}

  8. nth root - Wikipedia

    en.wikipedia.org/wiki/Nth_root

    A square root of a number x is a number r which, when squared, becomes x: =. Every positive real number has two square roots, one positive and one negative. For example, the two square roots of 25 are 5 and −5. The positive square root is also known as the principal square root, and is denoted with a radical sign:

  9. Negative number - Wikipedia

    en.wikipedia.org/wiki/Negative_number

    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 value. Negative numbers are usually written with a minus sign in front. For example, −3 represents a negative quantity with a magnitude of ...