Quadratic Equation Solver

Solve any quadratic equation ax² + bx + c = 0 with step-by-step working and graph.

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Quadratic Equation Solver
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How to use Quadratic Equation Solver

A quadratic equation is any equation in the form ax² + bx + c = 0, where a is not zero. These appear across mathematics, physics, engineering, economics, and computer science. The solver finds the roots (solutions) of any quadratic equation and shows the complete working, including the graph of the parabola. Entering coefficients: Enter the values of a, b, and c from your equation. For example, for 2x² − 5x + 3 = 0, enter a = 2, b = −5, c = 3. Fractional and decimal coefficients are supported. Click Solve. What the solver shows: Discriminant (b² − 4ac) — determines the nature of the roots before calculating them: Positive: two distinct real roots Zero: one repeated real root (the parabola touches the x-axis at one point) Negative: two complex (imaginary) conjugate roots (the parabola does not cross the x-axis) Roots (x₁ and x₂) — calculated using the quadratic formula: x = (−b ± √discriminant) / 2a. Exact simplified forms shown where possible, decimal approximations always included. Vertex — the turning point of the parabola. x-coordinate = −b / 2a; y-coordinate = f(x-vertex). Axis of symmetry — the vertical line x = −b / 2a that the parabola is symmetric around. Graph — a plot of the parabola showing the x-axis intercepts (if they exist), vertex, and axis of symmetry. Step-by-step working: Each step of the quadratic formula application is shown — substitution, discriminant calculation, square root, and final root calculation. Useful for homework, exam preparation, and understanding the process. Common applications: projectile motion (height as a function of time), optimizing revenue and profit functions, finding intersection points, and solving geometric problems involving areas.

Frequently Asked Questions

What does the discriminant tell me about the roots?

The discriminant is b² − 4ac. If it is positive, the equation has two distinct real roots (the parabola crosses the x-axis twice). If it is zero, there is exactly one real root (the parabola touches the x-axis at its vertex). If it is negative, there are two complex conjugate roots and no real solutions (the parabola does not intersect the x-axis).

How does the solver handle complex (imaginary) roots?

When the discriminant is negative, the square root is imaginary. The solver shows the roots in complex form: x = p ± qi, where p = −b/2a (the real part) and q = √|discriminant| / 2a (the imaginary part). Complex roots of polynomials with real coefficients always come in conjugate pairs — if p + qi is a root, so is p − qi.

Can the solver handle equations where a = 0?

No. When a = 0, the equation becomes linear (bx + c = 0), not quadratic. The quadratic formula requires a ≠ 0 because dividing by 2a would mean dividing by zero. For linear equations, use basic algebra: x = −c/b. The solver will notify you if a = 0 is entered and decline to apply the quadratic formula.

What is the vertex of a parabola?

The vertex is the highest or lowest point of the parabola — the minimum if a > 0 (opens upward) or the maximum if a < 0 (opens downward). Its x-coordinate is −b/(2a), and its y-coordinate is the value of the equation at that x. The vertex represents the optimal value in optimization problems — maximum profit, minimum cost, peak height in projectile motion.

How do I convert a quadratic in vertex form to standard form for the solver?

Vertex form is y = a(x − h)² + k. Expand it: multiply out a(x − h)² to get a(x² − 2hx + h²) = ax² − 2ahx + ah². Then add k. The standard form coefficients are a = a, b = −2ah, and c = ah² + k. Enter these values into the solver to find the roots of the original equation.

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