Quadratic Formula Calculator – Guide & Formulas
Solve any quadratic equation using the quadratic formula. Calculates real and complex roots, vertex coordinates, and displays step-by-step discriminant steps.
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Put these formulas into practice with our instant, step-by-step Quadratic Formula Calculator.
Free online **quadratic formula calculator** — solve any **quadratic equation ax² + bx + c = 0** instantly with step-by-step work. Our **quadratic solver** calculates **real and complex roots**, the **discriminant**, and the **parabola vertex coordinates**. Whether you need a **quadratic equation calculator** for algebra homework or a **quadratic formula solver** for engineering, this tool provides accurate results with detailed explanations of every step.
Key Takeaway
Use the free Quadratic Formula Calculator to solve any quadratic equation using the quadratic formula. calculates real and complex roots, vertex coordinates, and displays step-by-step discriminant steps. Get instant results with step-by-step explanations.
How to Use the Quadratic Formula Calculator
- Enter the coefficient "a" (the x² term — must not equal 0).
- Enter the coefficient "b" (the x term) and the constant "c".
- Click Calculate to solve the equation using the quadratic formula.
- Review the discriminant value to determine the number and type of roots.
- Examine the step-by-step solution, vertex coordinates, and axis of symmetry.
The Formula
Variable Definitions
- a: The leading coefficient (coefficient of x²)
- b: The linear coefficient (coefficient of x)
- c: The constant term
- b² - 4ac: The discriminant — determines the nature and number of roots
- ±: Plus-or-minus — indicates two solutions when discriminant is positive
Solving x² - 5x + 6 = 0
A student needs to find the solutions to the equation where a = 1, b = -5, and c = 6.
- Step 1: Identify coefficients: a = 1, b = -5, c = 6.
- Step 2: Calculate the discriminant: (-5)² - 4(1)(6) = 25 - 24 = 1.
- Step 3: Since the discriminant is positive (1 > 0), there are 2 distinct real roots.
- Step 4: Apply the formula: x = (5 ± √1) / (2·1) = (5 ± 1) / 2.
- Step 5: The two solutions are x = (5 + 1)/2 = 3 and x = (5 - 1)/2 = 2.
Financial Advisory Notice
This Quadratic Formula Calculator provides mathematical solutions for educational and problem-solving purposes only. While the formulas and algorithms are verified for accuracy, users should verify critical calculations independently.
Frequently Asked Questions
What does the discriminant (b² - 4ac) tell us?
If the discriminant > 0, there are two distinct real roots. If = 0, there is exactly one repeating real root. If < 0, there are two complex (imaginary) conjugate roots.
What is the vertex of a quadratic function?
The vertex is the minimum or maximum point of the parabola. The x-coordinate is found with -b/(2a), and the y-coordinate is the function value at that x.
Can coefficient "a" be zero?
No. If a = 0, the equation becomes linear (bx + c = 0) and is not a quadratic equation. The quadratic formula is undefined when a = 0.
How do I solve by factoring instead of the formula?
Factor the quadratic into two binomials and set each equal to zero. For x² - 5x + 6 = 0, factor to (x - 2)(x - 3) = 0, giving x = 2 and x = 3.
What is completing the square?
Completing the square is a method that rearranges the equation into the form (x - h)² = k, from which solutions can be found by taking square roots. It is the derivation basis for the quadratic formula.
How do complex roots work?
When the discriminant is negative, the square root produces imaginary numbers. Complex roots always come in conjugate pairs: a + bi and a - bi.
What is the axis of symmetry?
The axis of symmetry is the vertical line x = -b/(2a) that passes through the vertex. It divides the parabola into two mirror-image halves.
How do I find the y-intercept of a quadratic?
The y-intercept is the value of the function when x = 0, which is simply the constant term c.
What is the sum and product of roots formula?
For ax² + bx + c = 0, the sum of roots = -b/a and the product of roots = c/a. These follow directly from Vieta's formulas.
Can a quadratic have no real solutions?
Yes. When the discriminant is negative, the equation has no real solutions — only two complex conjugate solutions. The parabola does not cross the x-axis.
What is the difference between the vertex form and standard form?
Standard form is ax² + bx + c, while vertex form is a(x - h)² + k where (h, k) is the vertex. Vertex form makes it easy to identify the vertex and direction of opening.
How do I graph a quadratic equation?
Plot the vertex, the y-intercept, the x-intercepts (if they exist), and the axis of symmetry. Connect these points with a smooth U-shaped curve (parabola).
What are real vs complex roots?
Real roots are numbers that can be plotted on the number line. Complex roots involve the imaginary unit i and cannot be plotted on the real number line.
Why is the quadratic formula important?
The quadratic formula provides a universal method to solve ANY quadratic equation, even when factoring is difficult or impossible. It works for all cases: two real roots, one repeated root, or two complex roots.
How do I check if my quadratic solutions are correct?
Substitute each solution back into the original equation. If both sides equal zero, your solutions are correct.
What is a repeated root?
A repeated root (or double root) occurs when the discriminant equals zero. The parabola touches the x-axis at exactly one point — the vertex.
How does the value of "a" affect the parabola?
A positive "a" opens the parabola upward (minimum vertex). A negative "a" opens it downward (maximum vertex). Larger |a| values make the parabola narrower.
What are the x-intercepts of a quadratic?
X-intercepts are the points where the parabola crosses the x-axis — these are the real roots of the equation ax² + bx + c = 0.
Is this quadratic formula calculator accurate?
Yes. This calculator uses precise arithmetic to solve quadratic equations and provides step-by-step explanations so you can verify each calculation.