Quadratic Equation Solver
Solve any quadratic equation ax² + bx + c = 0 with step-by-step working and graph.
How to use Quadratic Equation Solver
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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