No solution refers to the number that does not satisfy the equation within a certain range. No solution is not no real root (no real solution). The mathematical range we know now is complex number (including real number and imaginary number). For example, whm9999 has an example: x 2 =- 1. There is no solution in the real number range (no real number solution), but it can never be said that there is a solution in the imaginary circle or a wider range, where I is the imaginary unit.

The most typical unsolvable equation is 1/x=0. There is still no solution in the complex value domain. Some people may say that the solution is x=∞. In fact, ∞ is only a symbol, not a number, so it cannot be used as a solution.