Maths Calculators

Quadratic Formula Calculator

Solve quadratic equations and calculate their real or complex roots using the quadratic formula.

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Quadratic Formula Calculator

Enter the coefficients a, b and c from a quadratic equation in the form ax² + bx + c = 0.

ax² + bx + c = 0
The coefficient of x². It cannot be zero.
The coefficient of x.
The constant term.
F-Secure

What Is a Quadratic Formula Calculator?

A Quadratic Formula Calculator is an online maths tool that solves quadratic equations by applying the standard quadratic formula. A quadratic equation has the general form ax² + bx + c = 0, where a, b and c are numerical coefficients and a cannot equal zero.

This calculator is useful for students, teachers, engineers and anyone working with algebra or equations. Enter the three coefficients and the calculator determines the discriminant, calculates the roots and shows the working used to obtain the result.

Why Use Quadratic Formula Calculator?

The calculator performs the quadratic formula calculation instantly while showing the important intermediate values, making it useful for checking answers as well as solving equations.

1

Two Real Roots

Identifies and calculates two distinct real solutions when the discriminant is positive.

2

Repeated Roots

Recognises when the discriminant is zero and calculates the single repeated real root.

3

Complex Roots

Calculates complex conjugate roots when the discriminant is negative.

4

Decimal Values

Accepts decimal coefficients for calculations involving non-integer equations.

5

Negative Coefficients

Works with positive and negative values for a, b and c.

6

Shows the Working

Displays the discriminant and formula substitution so you can follow the calculation.

How to Use Quadratic Formula Calculator

To solve a quadratic equation, first identify the coefficients a, b and c, then enter them into the corresponding fields.

  1. Enter coefficient a — Enter the number multiplying x². This value must not be zero.
  2. Enter coefficient b — Enter the number multiplying x.
  3. Enter coefficient c — Enter the constant term in the equation.
  4. Calculate the roots — Select Calculate Roots to display the discriminant, solutions and calculation steps.

Calculate Quadratic Equation Roots

The quadratic formula provides a general method for finding the solutions of any quadratic equation that can be written as ax² + bx + c = 0, provided that a ≠ 0. The formula is x = (-b ± √(b² − 4ac)) / (2a). The plus and minus symbols produce the two possible solutions.

For example, consider the equation x² − 5x + 6 = 0. Here, a = 1, b = −5 and c = 6. Substituting these values into the formula gives a discriminant of 1 and produces the two roots x = 2 and x = 3.

Understanding the Discriminant

The discriminant is the part of the quadratic formula under the square root: b² − 4ac. Its value indicates the nature and number of the equation's roots. A positive discriminant produces two distinct real roots, a zero discriminant produces one repeated real root, and a negative discriminant produces two complex conjugate roots.

Real and Complex Solutions

When the discriminant is positive, both solutions are real numbers. When it is exactly zero, the two solutions are identical. When the discriminant is negative, the square root involves an imaginary number, so the solutions are expressed using the imaginary unit i, where i² = −1.

Quadratic Formula Calculator Information

The value of a must not be zero because an equation with a = 0 is no longer quadratic. If a is zero, the equation becomes linear and requires a different method of solving.

The calculator accepts integers, negative numbers and decimal coefficients. Results are displayed using a practical decimal precision to avoid showing unnecessary floating-point digits. For negative discriminants, the calculator reports the complex roots using real and imaginary components.

James William Steven Parker, creator of YesTools
Created by

James William Steven Parker

Creator & Developer of YesTools

James William Steven Parker is a web developer and technology professional with extensive experience in web development, web design, SEO, web hosting, systems analysis and cybersecurity. He created YesTools to provide fast, practical and free online tools for everyday tasks and technical work.

Learn more about James and YesTools

Frequently Asked Questions

The quadratic formula is x = (-b ± √(b² − 4ac)) / (2a). It is used to solve quadratic equations written in the form ax² + bx + c = 0.
Enter the values of a, b and c from your quadratic equation, then select Calculate Roots. The calculator displays the discriminant, roots and calculation steps.
The discriminant is b² − 4ac. A positive value gives two distinct real roots, zero gives one repeated real root, and a negative value gives two complex conjugate roots.
When the discriminant is zero, the quadratic equation has one repeated real root. The root is x = −b / (2a).
Yes. When the discriminant is negative, the calculator displays the two complex conjugate roots using their real and imaginary components.
Yes. You can enter positive, negative and decimal values for all three coefficients. The coefficient a must not be zero.

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