The square root of a negative number has no solution within the range of real numbers.
Mathematicians call the result of this operation imaginary numbers, because such operations cannot be explained within the range of real numbers, so They are called imaginary numbers.
A pair of real numbers and imaginary numbers is regarded as one number in the range of complex numbers and is named a complex number.
Therefore, real numbers become special complex numbers (missing the ordinal part) ), imaginary numbers also become special complex numbers (missing the real part).
The unit of imaginary numbers is i, i is the root minus 1.
3i is an imaginary number, which is the root (-3 ), that is, 3× root (-1)
2+3i is a complex number, (the real part is 2, the imaginary part is 3i)