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Quadratic Formula Solver

Our Quadratic Formula Solver helps you quickly find the roots of any quadratic equation in the standard form ax² + bx + c = 0. Just enter the coefficients a, b, and c, and let the calculator do the work, showing both real and complex solutions.

Enter the coefficient of x² (if 0, solves as a linear equation).

Enter the coefficient of x.

Enter the constant term.

How it works

Our Quadratic Formula Solver helps you quickly find the roots of any quadratic equation in the standard form ax² + bx + c = 0. Just enter the coefficients a, b, and c, and let the calculator do the work, showing both real and complex solutions.


The Formula

The quadratic formula is:
x = [-b ± sqrt(b² - 4ac)] / 2a

Worked Example

  1. Example: Solve 2x² + 5x - 3 = 0

    For the equation 2x² + 5x - 3 = 0, we have a = 2, b = 5, and c = -3. 1. Calculate the discriminant: b² - 4ac = (5)² - 4(2)(-3) = 25 + 24 = 49. 2. Since the discriminant is positive (49 > 0), there are two distinct real roots. 3. Apply the quadratic formula: x = [-5 ± sqrt(49)] / (2*2) = [-5 ± 7] / 4. 4. The two roots are: x₁ = (-5 + 7) / 4 = 2 / 4 = 0.5, and x₂ = (-5 - 7) / 4 = -12 / 4 = -3.


Tips, Assumptions & Limitations

  • Ensure your quadratic equation is in the standard form ax² + bx + c = 0 before entering the coefficients.
  • If a = 0 and b ≠ 0, the tool falls back to the linear solution x = −c/b.
  • The vertex of the parabola is at (h, k) = (−b/(2a), f(−b/(2a))).
  • The discriminant (b² - 4ac) tells you the nature of the roots: positive means two real roots, zero means one real root, and negative means two complex roots.
FAQ

A quadratic equation is a polynomial equation of the second degree, meaning the highest power of the variable is 2. It is typically written in the standard form ax² + bx + c = 0, where 'a', 'b', and 'c' are coefficients and 'a' is not equal to zero.

The quadratic formula finds the solutions (roots) of any quadratic equation. For ax² + bx + c = 0, the roots are x = [-b ± √(b² - 4ac)] / 2a.

The discriminant is the part of the quadratic formula under the square root sign: b² - 4ac. Its value determines the nature of the roots of the quadratic equation. If positive, there are two real roots; if zero, there is one real root; if negative, there are two complex conjugate roots.

The vertex (h, k) is the turning point of the parabola y = ax² + bx + c. It is at h = −b/(2a) and k = a·h² + b·h + c. This calculator reports the vertex alongside the roots.

If a = 0 and b ≠ 0, the equation is linear (bx + c = 0) and the calculator returns x = −c/b. If both a and b are 0, it is not a valid linear or quadratic equation.

Yes, our Quadratic Formula Solver is designed to handle all types of roots, including complex conjugate roots. If the discriminant is negative, the calculator will display the solutions in the form of a + bi, where 'i' is the imaginary unit.

Companion article

Quadratic Formula Solver Explained: Master Quadratic Equations

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How this calculator works

Quadratic equations are a cornerstone of algebra, appearing in everything from physics to finance. They might look intimidating with that 'x²' term, but mastering them opens up a whole new world of problem-solving. Our Quadratic Equation Solver is here to simplify the process, helping you quickly find the solutions (roots) and key features like the vertex for any equation in the standard form ax² + bx + c = 0.

Explanation

A quadratic equation is a second-degree polynomial equation. This means the highest power of the variable (usually 'x') is 2. The standard form, ax² + bx + c = 0, is crucial because it sets up the equation for solving using the famous quadratic formula. Here, 'a', 'b', and 'c' are coefficients, with 'a' never being zero. If 'a' were zero, it would simply be a linear equation (bx + c = 0). The solutions to a quadratic equation are also known as its roots, and they represent the x-intercepts of the parabola when the equation is graphed.

Formula

The Quadratic Formula:
x = [-b ± √(b² - 4ac)] / 2a Where:
'a' is the coefficient of x²
'b' is the coefficient of x
'c' is the constant term And the Discriminant (Δ) is: Δ = b² - 4ac Also, the Vertex of the parabola (x_v, y_v) is found using:
x_v = -b / 2a
y_v = a(x_v)² + b(x_v) + c

Worked example

Let's work through an example: Solve the equation 2x² - 7x + 3 = 0. Here, a = 2, b = -7, and c = 3. First, calculate the discriminant: Δ = b² - 4ac = (-7)² - 4(2)(3) = 49 - 24 = 25 Since Δ > 0, we know there will be two distinct real roots. Now, apply the quadratic formula: x = [-(-7) ± √25] / (2 * 2) x = [7 ± 5] / 4 For x₁: (7 + 5) / 4 = 12 / 4 = 3 For x₂: (7 - 5) / 4 = 2 / 4 = 0.5 So, the roots are x = 3 and x = 0.5. To find the vertex: x_v = -b / 2a = -(-7) / (2 * 2) = 7 / 4 = 1.75 y_v = 2(1.75)² - 7(1.75) + 3 = 2(3.0625) - 12.25 + 3 = 6.125 - 12.25 + 3 = -3.125 The vertex is (1.75, -3.125).

How to use this tool

Using our Quadratic Equation Solver is straightforward. Simply enter the numerical values for the coefficients 'a', 'b', and 'c' into the respective input fields. Remember that 'a' cannot be zero for it to be a quadratic equation. If a term is missing (e.g., no 'x' term), enter 0 for its coefficient. Once you've entered the values, the calculator will instantly display the roots (solutions), indicating whether they are real or complex, along with the discriminant and the coordinates of the parabola's vertex.

Frequently asked questions

What's the difference between real and complex roots?
Real roots are numbers that can be plotted on a number line, while complex roots involve the imaginary unit 'i' (where i² = -1). Complex roots occur when the discriminant (b² - 4ac) is negative.
What does the vertex of a parabola represent?
The vertex is the highest or lowest point on the graph of a quadratic equation (a parabola). It represents the maximum or minimum value of the quadratic function and is a key feature for understanding the graph's shape and position.
Can I use this calculator for linear equations?
While primarily designed for quadratic equations, if you enter 'a = 0', the calculator will treat it as a linear equation (bx + c = 0) and provide the single solution for x. However, for dedicated linear equation solving, other tools might be more appropriate.

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