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Quadratic Equation Solver

Type in a, b, and c — Axiom shows every step, starting with the discriminant.

a x² + b x + c = 0

How to use this calculator

Rearrange the equation into ax² + bx + c = 0 and enter a, b, and c with their signs. Press Solve step-by-step to see the discriminant and real solutions; a must be nonzero.

How the calculation works

The discriminant D = b² − 4ac determines the real-root case: positive gives two roots, zero gives a repeated root, and negative gives no real roots. The quadratic formula is x = (−b ± √D)/(2a). This solver uses that formula rather than a separate factoring mode, with rounded decimals for numerical roots.

Worked examples

  1. 1. Find two real roots

    Enter 1, −5, 6 for x² − 5x + 6 = 0. D = 25 − 24 = 1, so x = (5 ± 1)/2 gives 2 and 3. Substituting either value makes the equation zero.

  2. 2. Recognize a repeated root

    For x² − 6x + 9 = 0, enter 1, −6, 9. D = 36 − 36 = 0, giving x = 6/2 = 3. The curve touches the x-axis at that root.

  3. 3. Recognize no real roots

    For x² + 1 = 0, enter 1, 0, 1. D = −4, so there are no real solutions. Complex roots exist, but this tool does not output them.

Frequently asked questions

What if my equation is not equal to zero?

Move all terms to one side first. For x² = 5x − 6, enter the equivalent equation x² − 5x + 6 = 0, using 1, −5, and 6.

Can the coefficient a be zero?

No. Removing x² makes the equation linear. Use the Linear Equation Solver for that case instead.

Does the calculator show complex roots?

No. A negative discriminant produces a no-real-solutions message. It does not mean the equation has no solutions over the complex numbers.

Can I check the roots by factoring?

If it factors cleanly, you can verify a result by hand: x² − 5x + 6 = (x − 2)(x − 3), so the roots are 2 and 3. This calculator does not factor the equation; it finds real roots with the quadratic formula.

Are decimal roots exact?

No. The formula is the symbolic expression, while displayed decimal roots are approximations. A near-zero discriminant may be treated as zero within floating-point precision.

Keep learning with related tools

Plot the same coefficients in the graphing calculator to connect roots with x-intercepts. For first-degree equations use the linear solver, and read the quadratic equations lesson for the reasoning behind the formula. Related tools: Linear & Quadratic Graphing Calculator, Linear Equation Solver. Read the Quadratic Equations lesson or practice quadratic equations to build confidence without relying on a calculator.