How can we prove that 4 is a complex number?

Question

We know 4 is a real number but how can we prove that it is a complex number? How can be describe it in the a+ib form??

Answer 1

What is your definition of complex number? Does $4+0i$ fit it? Some people think of complex number as in opposition to reals, in the way irrationals do not include the rationals, but the usual definition includes the reals.

Answer 2

Since real numbers is a subset of complex numbers therefore we can say that four is also a complex number. The four can be written as 4+0$i$.