section_path: Examples/Parameters and unknowns
section_name: Parameters and unknowns
paragraph_text: Parameters and unknowns
  
  Equations often contain terms other than the unknowns. These other terms, which are assumed to be known, are usually called constants, coefficients or parameters.
  
  An example of an equation involving x and y as unknowns and the parameter R is
  
  When R is chosen to have the value of 2 (R = 2), this equation would be recognized in Cartesian coordinates as the equation for the circle of radius of 2 around the origin. Hence, the equation with R unspecified is the general equation for the circle.
  
  Usually, the unknowns are denoted by letters at the end of the alphabet, x, y, z, w,..., while coefficients (parameters) are denoted by letters at the beginning, a, b, c, d,.... For example, the general quadratic equation is usually written ax + bx + c = 0.
  
  The process of finding the solutions, or, in case of parameters, expressing the unknowns in terms of the parameters, is called solving the equation. Such expressions of the solutions in terms of the parameters are also called solutions.
  
  A system of equations is a set of simultaneous equations, usually in several unknowns for which the common solutions are sought. Thus, a solution to the system is a set of values for each of the unknowns, which together form a solution to each equation in the system. For example, the system
  
  has the unique solution x = −1, y = 1.