A complex number can be visually represented as a pair of numbers (a, b) forming a vector on a diagram called an Argand diagram, representing the complex plane. Re is the real axis, Im is the imaginary axis, and i is the imaginary unit which satisfies i2 = â1.
When discussing blood types, the two groupings most commonly used are the ABO (A, B, AB, O) and Rh (+, -) systems. The least common blood type in humans is Bombay (EXTREMELY râ¦are), which is a type O with missing H antigen. Otherwise, of the normal ABO and Rh typings, the least common group is AB-.
We know that A, B, AB and O are the four blood groups that can be Rh positive or negative (viz: A+, A-, B+, B-, AB+, AB-, O+ and O-). Among them, O+ is the most common; while AB-is the rarest blood type.