Roots of Quadratic Equation – Formula, Definition With Examples

Welcome to another insightful piece from Brighterly, your reliable partner in making math fun and easy for children. We understand that quadratic equations can seem like an intimidating topic, especially for young learners. They appear complex and multifaceted, yet they are essential for a robust understanding of mathematics and are applicable in a myriad of real-world scenarios, including physics, engineering, and even finance.

In this article, we will demystify the topic of quadratic equations by delving into their roots – the solutions that satisfy these equations. We will take an engaging, step-by-step approach to cover the fundamentals, from the definition and formula to examples that provide a practical understanding of the concept. By the end of this article, our young learners at Brighterly will be conversant with quadratic equations and confident in tackling them. Remember, the secret to mastering math is understanding and practice, and that’s what we’re here to foster!

What Are the Roots of a Quadratic Equation?

A quadratic equation is a second-order polynomial equation in a single variable x. It has a standard form of ax² + bx + c = 0. In this equation, x represents an unknown, and a, b, and c are constants with ‘a’ not equal to zero. The roots of this equation, often referred to as the zeros or solutions of the equation, are the values of ‘x’ that satisfy the equation.

Simply put, the roots of a quadratic equation are the points where the quadratic function, or parabola, intersects the x-axis. The number of roots that a quadratic equation has depends on the discriminant (b² – 4ac). If the discriminant is greater than zero, the equation has two distinct real roots. If it equals zero, the equation has exactly one real root. Finally, if the discriminant is less than zero, the quadratic equation has two complex roots.

Definition of a Quadratic Equation

The quadratic equation is a special type of equation in mathematics that has been studied for thousands of years. It represents a relationship between the variables and constants that constitute it. The general form of a quadratic equation is ax² + bx + c = 0, where ‘a’, ‘b’, and ‘c’ are constants, ‘a’ is not equal to zero, and ‘x’ is the variable.

The term ‘quadratic’ comes from the Latin word ‘quadratus’, which means ‘square’. This is because the variable in the equation is squared, which is the highest power in the equation. The quadratic equation is a second-degree polynomial since the highest exponent is two.

Definition of Roots of a Quadratic Equation

The roots of a quadratic equation are the values that solve the equation, or make it true. In terms of a graph, these roots correspond to the points where the parabola, or the shape of the graph of the equation, intersects the x-axis.

Essentially, if you plug the root values into the quadratic equation for the variable ‘x’, you will end up with a true statement, where both sides of the equation are equal. The process of finding these root values is referred to as solving the quadratic equation.

Properties of Quadratic Equations

Quadratic equations exhibit several unique properties that set them apart from other types of equations. For instance, their graphs always take on the shape of a curve known as a parabola. The axis of symmetry of a parabola is always a vertical line, and it passes through the vertex, or the ‘highest’ or ‘lowest’ point of the parabola.

Furthermore, the graph of a quadratic equation opens upwards if the coefficient ‘a’ in the equation is positive, and it opens downwards if ‘a’ is negative. This attribute of a quadratic equation gives it a minimum or maximum value, depending on the direction of the opening of the parabola.

Properties of Roots of Quadratic Equations

The roots of a quadratic equation are intrinsically linked to the equation’s properties and coefficients. The sum of the roots of a quadratic equation is equal to the negation of the coefficient ‘b’, divided by the coefficient ‘a’. This is commonly written as Sum = -b/a.

Moreover, the product of the roots is equal to the constant term ‘c’ divided by the coefficient ‘a’. This can be represented as Product = c/a. These properties allow for quick calculations of the roots when the quadratic equation is given in standard form.

Difference Between Roots of a Quadratic Equation

The roots of a quadratic equation can either be real or complex, depending on the value of the discriminant (b² – 4ac). If the discriminant is positive, there are two distinct real roots. If it’s zero, there’s exactly one real root. If it’s negative, there are two complex roots.

Moreover, the roots can also be rational or irrational. Rational roots can be expressed as a ratio of two integers, while irrational roots cannot. The nature of the roots can significantly impact the solutions to the equation and their representation.

The Quadratic Formula for Finding the Roots

The roots of a quadratic equation can be found using the quadratic formula. This formula, which is derived from the process of completing the square, is expressed as x = [-b ± sqrt(b² – 4ac)] / 2a.

In this formula, ‘a’, ‘b’, and ‘c’ are the coefficients of the quadratic equation, and ‘sqrt’ denotes the square root. The symbol ‘±’ indicates that there are typically two solutions, which correspond to the addition and the subtraction.

Using the Quadratic Formula to Find the Roots of an Equation

When using the quadratic formula to find the roots of an equation, the first step is to identify the coefficients ‘a’, ‘b’, and ‘c’ in the equation. Then, plug these values into the formula and perform the operations.

The discriminant, or b² – 4ac, determines the nature of the roots. If the discriminant is positive, you’ll get two distinct real roots. If it’s zero, you’ll get one real root. And if it’s negative, you’ll get two complex roots.

Writing Quadratic Equations Given the Roots

If the roots of a quadratic equation are given, you can write the equation by using the general form x² – (sum of roots)x + (product of roots) = 0. This can be helpful in many mathematical and real-world problems.

For instance, if the roots are 3 and 2, the sum of the roots is 5, and the product is 6. Therefore, the quadratic equation is x² – 5x + 6 = 0.

Practice Problems on Roots of Quadratic Equations

Practicing quadratic equations and understanding their roots is crucial for mastering them. Here are a few practice problems:

  1. Find the roots of the equation x² – 5x + 6 = 0.
  2. Given the roots of the equation are 4 and -2, write the quadratic equation.
  3. Determine the nature of the roots of the equation 2x² – 4x + 5 = 0.


We hope this comprehensive guide on the roots of quadratic equations has been illuminating and has made this essential mathematical topic less daunting for our young learners at Brighterly. Remember, understanding the roots of a quadratic equation is a fundamental step in mastering algebra and mathematics in general.

Equipped with the knowledge of the definition, formula, properties, and the ways to solve quadratic equations, you’re now ready to tackle any problem that comes your way. As always, practice is paramount. Try as many problems as you can to solidify your understanding.

At Brighterly, our mission is to simplify complex concepts and make learning an exciting journey. As you continue to delve into math, remember to approach each new concept with an open mind, readiness to learn, and of course, a pinch of fun. Stay tuned for more insightful content, and keep shining brightly in your mathematical journey!

Frequently Asked Questions on Roots of Quadratic Equations

Can a quadratic equation have only one root?

Yes, a quadratic equation can indeed have only one real root. This unique scenario occurs when the discriminant, the part of the quadratic formula under the square root (b² – 4ac), is equal to zero. When this happens, the ‘±’ in the quadratic formula doesn’t create two different solutions, but instead, gives the same result twice. The single root is often referred to as a repeated or double root. It means that the graph of the quadratic equation touches the x-axis at one point.

Can quadratic equations have complex roots?

Yes, quadratic equations can definitely have complex roots. If the discriminant of a quadratic equation (b² – 4ac) is a negative number, then the roots of the equation will be complex. These roots are of the form a ± bi, where a and b are real numbers, and i is the imaginary unit, with the property that i² = -1. Complex roots usually come in pairs, and they are vital in fields such as electrical engineering and quantum physics.

What are real and complex roots?

Real roots and complex roots are solutions to the quadratic equation. Real roots are solutions that are real numbers. They could be rational (like 2, -1/2, or 0) or irrational (like √2 or √5). Complex roots, on the other hand, are solutions that involve ‘i’, the square root of -1. These roots have a real part and an imaginary part. They are often used in fields where we need to model oscillations or waves.

Why do we need to find the roots of a quadratic equation?

Finding the roots of a quadratic equation is essentially solving the equation. It gives us the x-values for which the equation holds true. In practical terms, these roots can represent critical points or solutions in various real-world situations. For instance, in physics, the roots of a quadratic equation could represent the times at which an object hits the ground. In business, they could represent break-even points. So, understanding how to find these roots is not only vital for math but also for understanding the world around us!

Information Sources:
  1. Quadratic Equation – Wolfram MathWorld
  2. Quadratic Functions – Brigham Young University
  3. Quadratic Equations – US Department of Education

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