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# What is a non-real number?

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### Quick Answer

**A non-real, or imaginary, number is any number that, when multiplied by itself, produces a negative number.** Mathematicians use the letter "i" to symbolize the square root of -1. An imaginary number is any real number multiplied by i. For example, 5i is imaginary; the square of 5i is -25.

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No real negative number can have a negative square root, because even a negative number multiplied by itself produces a positive product. Real numbers are those numbers that represent a quantity along a number line, including all positive and negative numbers and zero. Irrational numbers, even though they cannot be expressed as a precise fraction or decimal, are considered real numbers because they do exist at some place on the number line, even if that place is not precisely defined.

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Q:
## Which are allowable sets of quantum numbers?

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Full Answer >**Quantum numbers are used to describe the energy and shape of an electron orbital within an atom.**These numbers are represented by the letters n, l, m and s. The energy level quantum number, represented by the letter n, represents the energy of the electron within the orbital. This number can be equal to (1,2,3,4...). The higher the number, the further away the orbital is from the nucleus.Filed Under: -
Q:
## Is zero a perfect square?

A:There is some dispute as to whether zero is a perfect square. It meets most definitions of a perfect square, namely that it is an integer squared. However, it does not meet the historical definition of a perfect square, which involves arranging objects in a square shape.

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Q:
## What is Phi in math?

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Full Answer >**Phi is the 21st letter of the Greek alphabet and in mathematics, it is used as a symbol for the golden ratio.**The golden ratio refers to a special number that is approximately equal to 1.618. It is also known as the golden section, golden mean, divine section, medial proportion, golden cut, extreme and mean ratio, golden number or divine proportion.Filed Under: -
Q:
## Is the number 121 a prime number?

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Full Answer >**The number 121 is not a prime number.**A prime number must have only two factors, 1 and the number itself. However, the number 121 has three factors as 11 is a also factor of 121 in addition to 1 and 121 itself.Filed Under: