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The cube of a number n is denoted n 3, using a superscript 3, [a] for example 2 3 = 8. The cube operation can also be defined for any other mathematical expression, for example (x + 1) 3. The cube is also the number multiplied by its square: n 3 = n × n 2 = n × n × n. The cube function is the function x ↦ x 3 (often denoted y = x 3) that
Nicolas Chuquet used a form of exponential notation in the 15th century, for example 12 2 to represent 12x 2. [11] This was later used by Henricus Grammateus and Michael Stifel in the 16th century. In the late 16th century, Jost Bürgi would use Roman numerals for exponents in a way similar to that of Chuquet, for example iii 4 for 4 x 3 .
For each integer n > 2, the function n x is defined and increasing for x ≥ 1, and n 1 = 1, so that the n th super-root of x, , exists for x ≥ 1. However, if the linear approximation above is used, then y x = y + 1 {\displaystyle ^{y}x=y+1} if −1 < y ≤ 0 , so y y + 1 s {\displaystyle ^{y}{\sqrt {y+1}}_{s}} cannot exist.
[2] [3] In the 1970s Askold Khovanskii developed the theory of fewnomials that generalises Descartes' rule. [4] The rule of signs can be thought of as stating that the number of real roots of a polynomial is dependent on the polynomial's complexity, and that this complexity is proportional to the number of monomials it has, not its degree.
However, for any degree there are some polynomial equations that have algebraic solutions; for example, the equation = can be solved as =. The eight other solutions are nonreal complex numbers , which are also algebraic and have the form x = ± r 2 10 , {\displaystyle x=\pm r{\sqrt[{10}]{2}},} where r is a fifth root of unity , which can be ...
A negative real number −x has no real-valued square roots, but when x is treated as a complex number it has two imaginary square roots, + and , where i is the imaginary unit. In general, any non-zero complex number has n distinct complex-valued n th roots, equally distributed around a complex circle of constant absolute value .
On the negative numbers, numbers with greater absolute value have greater squares, so the square is a monotonically decreasing function on (−∞,0]. Hence, zero is the (global) minimum of the square function. The square x 2 of a number x is less than x (that is x 2 < x) if and only if 0 < x < 1, that is, if x belongs to the open interval (0,1).
For example, when computing x 2 k −1, the binary method requires k−1 multiplications and k−1 squarings. However, one could perform k squarings to get x 2 k and then multiply by x −1 to obtain x 2 k −1. To this end we define the signed-digit representation of an integer n in radix b as