: "The upper part is singular and the lower part is plural."

Gao Jian: "The upper part is singular and the lower part is plural."

Pants are singular above and plural below.

Note: One day, the teacher told everyone about singular and plural. Nick didn't listen carefully in his seat, so the teacher deliberately asked Nick, "Do you know singular and plural?" Nick immediately replied, "I see." The teacher asked him again, "Tell me, is' pants' singular or plural?" Nick said confidently, "The upper part of trousers is singular, and the lower part is plural."

Odd number is another name for positive number and odd number in mathematics. Mathematically, as opposed to even numbers (positive even numbers), it can be expressed as 2n+ 1 (n is an integer greater than or equal to 0).

We call a number in the form of z = a+bi (both a and b are real numbers) a complex number. Where a is called the real part, b is called the imaginary part, and I is called the imaginary part. When the imaginary part b of z = 0, then z is a real number; When the imaginary part of z. When b≠0 and the real part A = 0, Z is often called pure imaginary number. Complex number field is an algebraic closure of real number field, that is, any polynomial with complex coefficients always has roots in complex number field.

The complex number was first put forward by Cardan, a scholar in Milan, Italy, in the16th century. Through the work of D'Alembert, De Moivre, Euler and Gauss, this concept was gradually accepted by mathematicians.

The earliest literature on the roots of complex numbers comes from Helen, a Greek mathematician in the 1 th century. She thinks that a flat-topped pyramid is impossible.