Quadratic Equation – Definition with Examples

Welcome to the Brighterly, your trusted resource for comprehensive math education! In this blog post, we’ll venture into the captivating world of quadratic equations — a fundamental mathematical concept ubiquitous in many scientific disciplines. As with any field, the basics form the bedrock of understanding, and there’s nothing more fundamental in algebra than quadratic equations. We’ve designed this blog post to be your complete guide, explaining everything you need to know about quadratic equations and their significance.

From defining what a quadratic equation is, exploring its roots, understanding the discriminant, to the nature of roots, we’ve got you covered. We’ll journey through mathematical concepts with real-life applications and provide illustrative examples to ensure you grasp the essence. Furthermore, we’ll guide you through the various techniques to solve these equations, including the much-revered quadratic formula, solving by factorization, and completing the square.

What is a Quadratic Equation?

A quadratic equation is a second-order polynomial equation that takes the standard form ax^2 + bx + c = 0. It’s a fundamental concept that’s used extensively in numerous fields, from pure mathematics to physics and engineering. It is characterized by three components:

  1. ax^2 — This is the quadratic term, where a is the coefficient, and it can’t be zero, because if it were, the equation wouldn’t be quadratic anymore.
  2. bx — This is the linear term, with b as the coefficient.
  3. c — This is the constant term, which doesn’t have an x.

Each letter a, b, and c in the quadratic equation represents known numbers, with a ≠ 0. The variable x represents the unknown that we aim to solve for.

A fascinating characteristic of quadratic equations is that they always produce a curve called a parabola when graphed. You might have seen this curve in many real-life applications, such as the trajectory of a thrown ball.

Roots of a Quadratic Equation

The roots of a quadratic equation are the values of x that satisfy the equation, making it equal to zero. They’re also known as solutions or zeroes of the equation. They can be real (both positive and negative), imaginary, or even one of each! Determining the roots is a core part of solving quadratic equations, and the nature of these roots plays a significant role in understanding the solution’s behavior.

What Is Discriminant?

The discriminant in a quadratic equation is a function that helps determine the nature of the roots of the equation. It’s denoted by D or Δ, and it’s calculated using the formula D = b^2 - 4ac.

In simple terms, the discriminant tells us the number of solutions and their type (real or complex). If the discriminant is positive, we have two distinct real roots. If it’s zero, there’s exactly one real root (also called a repeated root). And if the discriminant is negative, we have two complex roots.

Nature of Roots of a Quadratic Equation

The nature of the roots of a quadratic equation can be determined by evaluating the discriminant D = b^2 - 4ac. It tells us whether the roots are real, repeated, or complex:

  • When D > 0, there are two distinct real roots.
  • When D = 0, there’s exactly one real root (also known as a repeated root).
  • When D < 0, there are two complex roots.

These rules provide us with a systematic way of determining the nature of roots even without finding the exact roots.

Nature of Roots – Video Lesson

Visual learners may benefit from our comprehensive video lesson, which elaborates on the nature of roots in a quadratic equation. With clear illustrations and step-by-step explanations, you can easily understand how the nature of roots is determined.

How to Determine the Nature of the Roots of a Quadratic Equation?

The nature of roots in a quadratic equation can be determined using the discriminant. The following steps can help in determining the nature of roots:

  1. Identify the coefficients a, b, and c in the quadratic equation.
  2. Calculate the discriminant using the formula D = b^2 - 4ac.
  3. Analyze the result: If D > 0, the equation has two distinct real roots; if D = 0, the equation has one repeated real root; if D < 0, the equation has two complex roots.

With these steps, we can identify the nature of roots without actually solving the quadratic equation.

Quadratic Formula

The quadratic formula is a powerful tool that provides the solution to any quadratic equation. The formula is x = [-b ± sqrt(D)] / 2a, where D is the discriminant of the quadratic equation. It allows us to compute the roots directly.

This formula can handle any type of roots, be they real, repeated, or complex. Thus, it’s a universal method for solving quadratic equations.

Proof of Quadratic Formula

The proof of the quadratic formula can be done using the method of completing the square, which involves rearranging the quadratic equation into a perfect square trinomial. We won’t go into the nitty-gritty of the proof here, but you can find a step-by-step guide in our complete proof tutorial.

Nature of Roots of the Quadratic Equation

Understanding the nature of roots in a quadratic equation provides insights into the structure of the equation and the behavior of its graph. The discriminant, D = b^2 - 4ac, is used to analyze the nature of roots. A positive D gives two distinct real roots, D equal to zero results in one real root (or a repeated root), while a negative D results in two complex roots.

Discriminant: D = b^2 – 4ac

The discriminant, denoted by D or Δ, is computed using the formula D = b^2 - 4ac. It plays a critical role in determining the number and nature of roots for a quadratic equation.

When D > 0, the quadratic equation has two distinct real roots. When D = 0, there’s one real root (also called a repeated root). When D < 0, there are two complex roots.

Sum and Product of Roots of Quadratic Equation

The sum and product of roots of a quadratic equation hold certain properties:

  • The sum of the roots, often represented as α + β, equals -b/a.
  • The product of the roots, represented as α * β, equals c/a.

These properties come in handy when we need to find the quadratic equation given the roots or find the roots given the coefficients.

Writing Quadratic Equations Using Roots

To write a quadratic equation using roots, we can use the sum and product of roots properties. If we know the roots α and β, we can write the equation as x^2 - (α + β)x + αβ = 0.

By knowing the roots, we can construct the corresponding quadratic equation without having to deal with a specific problem’s complications.

Formulas Related to Quadratic Equations

Quadratic equations have a few related formulas that prove helpful in solving these equations:

  • Quadratic formula: x = [-b ± sqrt(b^2 - 4ac)] / 2a
  • Discriminant: D = b^2 - 4ac
  • Sum of roots: α + β = -b/a
  • Product of roots: αβ = c/a

These formulas allow us to solve any quadratic equation systematically.

Solving Quadratic Equations By Completing The Square Worksheets PDF

View pdf

Solving Quadratic Equations By Completing The Square Worksheets

Solving Quadratic Equations By Completing The Square Worksheet PDF

View pdf

Solving Quadratic Equations By Completing The Square Worksheet

At Brighterly, we believe that practice is the key to mastery. That’s why we invite you to explore our quadratic equation worksheets, where you can find an array of additional practice questions, complete with answers.

Methods to Solve Quadratic Equations

Quadratic equations can be solved using various methods, including:

  • Quadratic formula
  • Factorization
  • Completing the square
  • Graphical methods

Each method has its own pros and cons, and their applicability depends on the specific equation or situation.

Solving Quadratic Equations by Factorization

Solving quadratic equations by factorization involves rewriting the equation as a product of two binomial expressions set to zero. Once the equation is in this form, we can use the Zero Product Property, which states that if a product of factors equals zero, then at least one of the factors must be zero.

Method of Completing the Square

The method of completing the square involves transforming the quadratic equation into a perfect square trinomial. Once this transformation is done, it’s easier to solve for x. This method is also used in deriving the quadratic formula.

Quadratic Equations Having Common Roots

Quadratic equations can have common roots, which occur when the discriminants of two equations are equal. These common roots hold significant importance in many mathematical problems.

Maximum and Minimum Value of Quadratic Expression

A quadratic expression attains its maximum or minimum value at the vertex of its parabola. If a > 0, the parabola opens upwards and has a minimum value at the vertex, and if a < 0, the parabola opens downwards and has a maximum value at the vertex.

The x-coordinate of the vertex can be found using the formula -b/2a, and substituting this into the equation gives the maximum or minimum value.

Practice Questions on Quadratic Equation

Practicing is indeed the cornerstone of understanding and mastering quadratic equations. Here at Brighterly, we offer a plethora of practice questions that allow students to exercise their skills and reinforce their understanding. Each question is accompanied by detailed solutions, providing a step-by-step breakdown of how to approach and solve each problem. Below are a few examples of the type of questions you’ll find in our practice sets:

  1. Find the roots of the quadratic equation x^2 - 5x + 6 = 0. This question is meant to test your ability to factorize a quadratic equation and find its roots.

  2. Using the quadratic formula, solve 3x^2 - 4x - 7 = 0. This question challenges you to use the quadratic formula to find the roots, even when the equation is not easily factorizable.

  3. A quadratic equation has roots 3 and -2. Write the equation. This question asks you to apply the sum and product of roots properties to write the quadratic equation.

  4. If a quadratic equation ax^2 + bx + c = 0 has roots 4 and -1, find the value of a+b+c. This problem requires a solid understanding of the relationships between the coefficients and roots of a quadratic equation.

  5. Find the maximum value of the quadratic function f(x) = -2x^2 + 8x - 3. This question tests your ability to find the maximum or minimum value of a quadratic expression, a key skill in optimization problems.

And these are just the tip of the iceberg! Our practice set includes many more questions, including word problems, that make you apply your knowledge of quadratic equations in real-world situations. It’s always a good idea to regularly challenge yourself with these problems to get a solid grasp of the topic.

Remember, if you find yourself struggling with any question, our detailed solutions are there to guide you through the problem-solving process. So, don’t wait! Start practicing now, and see your understanding of quadratic equations grow!

Factoring Quadratic Equations Worksheet

Factoring Quadratic Equations Worksheet

Solving Quadratic Equations By Factoring Worksheet Answers

Solving Quadratic Equations By Factoring Worksheet Answers


In conclusion, quadratic equations are the heart and soul of algebra. They are essential for advancing in various mathematical and scientific fields, and their understanding opens the door to an array of other sophisticated mathematical concepts. At Brighterly, we strive to make learning an enlightening and enjoyable journey. We believe that this comprehensive guide to quadratic equations will provide you with the knowledge you need to tackle them with confidence.

Remember, the keys to mastering quadratic equations, or any mathematical concept, are understanding, practice, and patience. With Brighterly, you’re not alone on this journey. Our practice questions and additional resources are just a click away, designed to support and enhance your learning process. So keep exploring, keep asking questions, and keep learning, because the world is brighter when you do!

Frequently Asked Questions on Quadratic Equation

What are quadratic equations used for in real life?

Quadratic equations have numerous applications in real life. They are used in physics for motion and trajectory calculations, in engineering for design and optimization, in economics for cost and revenue modeling, and in many other fields. These equations provide a mathematical framework for solving problems involving variables that are squared.

Why do quadratic equations have two solutions?

Quadratic equations often have two solutions because they are second-degree polynomials, and the degree of a polynomial typically determines the maximum number of solutions it can have. The solutions are the points where the parabola (graph of the quadratic equation) crosses the x-axis.

Can a quadratic equation have complex roots?

Yes, a quadratic equation can have complex roots. If the discriminant of a quadratic equation (the part under the square root in the quadratic formula) is negative, then the equation will have two complex roots. These complex roots are still valid solutions to the equation and are often necessary when solving problems in fields like engineering and physics.

Why do we use the quadratic formula?

The quadratic formula is a universal solution for any quadratic equation. It is derived using the process of completing the square and provides a systematic way of finding the roots of any quadratic equation, regardless of whether the roots are real or complex.

What does the graph of a quadratic equation look like?

The graph of a quadratic equation forms a curve called a parabola. Depending on the sign of the coefficient of the squared term (a in ax^2 + bx + c), the parabola opens upwards (a > 0) or downwards (a < 0). The vertex (peak or valley) of the parabola represents the maximum or minimum value of the quadratic equation.

Information Sources
  1. Quadratic Equation – Wikipedia
  2. Quadratic Equations – SchoolYourself
  3. Quadratic Equation – Wolfram MathWorld

Math Catch Up Program

Image -Math Catch Up Program
  • Learn Math Simple - Fast - Effective
  • Overcome math obstacles and reach new heights with Brighterly.

Kid’s grade

  • Grade 1
  • Grade 2
  • Grade 3
  • Grade 4
  • Grade 5
  • Grade 6
  • Grade 7
  • Grade 8

Simple - Fast - Effective
Overcome math obstacles and reach new heights with Brighterly.

Select Your Grade
Table of Contents

Kid’s grade

  • Grade 1
  • Grade 2
  • Grade 3
  • Grade 4
  • Grade 5
  • Grade 6
  • Grade 7
  • Grade 8
Image full form