The only other complex number x satisfying the equation x2 = − 1 is − i . In the algebra of quaternions , containing the complex plane , the equation x2 = − 1 has an infinity of solutions .
The only other complex number x for which the equation x2 = − 1 holds is − i . In the algebra of quaternions , which has the complex plane , the equation x2 = − 1 has an infinity of solutions .