What is the square root of -4

When it comes to the concept of square roots, we’re often taught that the square root of a negative number is undefined. However, in the realm of complex numbers, we find that the square root of -4 is indeed a real number. Let’s explore this intriguing concept further.

Understanding Imaginary Numbers

Definition: An imaginary number is a complex number that can be written as a real number multiplied by the imaginary unit “i,” which is defined as the square root of -1. In other words, i2=-1.

Imaginary numbers are essential in mathematics, especially when dealing with problems involving square roots of negative numbers. They allow us to work with and solve equations that would be impossible to solve using only real numbers.

Dealing with the Square Root of -4

So, what is the square root of -4? The answer is 2i. Here’s why:

First, we express -4 as -1 * 4. Then, we take the square root of each factor. The square root of -1 is the imaginary unit “i”, and the square root of 4 is 2. Therefore, the square root of -4 is 2i.

Graphical Representation

One way to visualize the square root of -4 is to plot it on the complex plane. The complex plane has two axes: the x-axis represents the real part of the complex number, and the y-axis represents the imaginary part. The point (0, 2) on the complex plane represents the square root of -4.

Applications in Mathematics and Engineering

The concept of imaginary numbers and the square root of -4 has numerous applications in various fields, including mathematics and engineering. In electrical engineering, for example, imaginary numbers are used to represent electrical impedance in circuits. In mathematics, they are used in complex analysis and are fundamental to understanding and solving certain types of equations and problems.


While it may seem counterintuitive at first, the square root of -4 is indeed a real number in the realm of complex numbers. Imaginary numbers, represented by the imaginary unit “i,” play a crucial role in making this possible. Understanding and working with imaginary numbers expands our mathematical toolkit and allows us to solve a wider range of problems more effectively.

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