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Algebra Tool

Solve Quadratic Equations

Instantly find the roots of any quadratic equation ax² + bx + c = 0. Get step-by-step solutions including the discriminant.

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ax² + bx + c = 0

What is a Quadratic Equation?

A quadratic equation is a polynomial equation of the second degree. The standard form of a quadratic equation is:

ax² + bx + c = 0

Where:

  • x is the variable or unknown.
  • a, b, and c are constants (real numbers) where a is not equal to 0.

The Quadratic Formula

To find the roots (solutions) for x, we use the quadratic formula:

Quadratic Formula

Understanding the Discriminant

The term inside the square root, b² - 4ac, is called the discriminant (symbol: Δ). It tells us the nature of the roots:

  • If Δ > 0: The equation has two distinct real roots.
  • If Δ = 0: The equation has exactly one real root (a repeated root).
  • If Δ < 0: The equation has no real roots (the roots are complex/imaginary numbers).

Frequently Asked Questions

Can "a" be zero?

No. If a = 0, the equation becomes a linear equation (bx + c = 0), not a quadratic one. Our calculator will warn you if you input 0 for a.

What if the roots are imaginary?

Currently, this calculator specializes in finding real roots for practical applications. If the discriminant is negative, it will inform you that the roots are complex/imaginary but will not display the imaginary parts.

How do I factor a quadratic equation?

Sometimes factoring is faster than the formula. You look for two numbers that multiply to ac and add to b. If factoring is difficult, the quadratic formula always works!