What is a equation that has no solution?

Answer 1

Here are a few:

0 = 1

x = x + 1 (subtract "x" on each side, and you get the previous one!)

x2 = -1 (if you want real numbers; however, it has two solutions in the complex numbers)

ln x = -1 (same as above: no solution in the real numbers, but it has a solution in the complex numbers)

ln x = 0 (no solution, neither in the real numbers, nor in the complex numbers)

0x = 5