Bring radical

The Bring radical, also called the ultraradical, is a function that gives the unique real root of the polynomial equation x^5 + x + a, defining x as an algebraic function of a. It is the simplest algebraic function that cannot be expressed using ordinary radicals, meaning root-extraction operations alone. It is named after the Swedish mathematician Erland Bring, who introduced it in the eighteenth century; later, George Jerrard showed that certain quintic equations can be solved using ordinary radicals together with the Bring radical, by transforming a general quintic into a simplified normal form. Because the Abel-Ruffini theorem rules out a general radical solution for quintic equations, the Bring radical supplies the extra tool needed to give quintics a closed form solution, in the same way that other special functions provide closed forms for equations that ordinary radicals alone cannot solve. This description is adapted from Wikipedia contributors under CC BY-SA 4.0; changes were made. https://creativecommons.org/licenses/by-sa/4.0/