 If the solutions are required to be "positive" integers ("x" > 0, "y" > 0), only a finite number of solutions may be possible.This restriction on the acceptable solutions allows some systems of Diophantine equations with more unknowns than equations to have a finite number of solutions; this is impossible for a system of linear equations when the solutions can be any real number (see Underdetermined system).A finite field is a set of numbers with four generalized operations.