Formula Calculator

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Quadratic Formula Calculator

Discriminant (D):
Root 1 (x₁):
Root 2 (x₂):

How the Quadratic Formula Works

The quadratic formula is used to find the solutions (roots) of a quadratic equation. A quadratic equation is a second-order polynomial equation in a single variable x, expressed in the standard form:

ax² + bx + c = 0

Where a, b, and c are numerical coefficients. The formula to solve for x is:

x = [-b ± sqrt(b² – 4ac)] / 2a

Understanding the Discriminant

The value inside the square root, D = b² – 4ac, is known as the discriminant. It determines the nature of the roots:

  • D > 0: Two distinct real roots.
  • D = 0: One repeated real root.
  • D < 0: Two complex (imaginary) roots.

Step-by-Step Calculation Example

Suppose you have the equation x² – 5x + 6 = 0.

  1. Identify the coefficients: a = 1, b = -5, c = 6.
  2. Calculate the discriminant: (-5)² – 4(1)(6) = 25 – 24 = 1.
  3. Since D > 0, calculate the two roots:
  4. x₁ = (5 + sqrt(1)) / 2 = 3
  5. x₂ = (5 – sqrt(1)) / 2 = 2
function calculateQuadratic() { var a = parseFloat(document.getElementById('coeffA').value); var b = parseFloat(document.getElementById('coeffB').value); var c = parseFloat(document.getElementById('coeffC').value); var resArea = document.getElementById('resultArea'); var valDisc = document.getElementById('valDisc'); var valX1 = document.getElementById('valX1'); var valX2 = document.getElementById('valX2'); var msgType = document.getElementById('msgType'); if (isNaN(a) || isNaN(b) || isNaN(c)) { alert("Please enter valid numbers for all coefficients."); return; } if (a === 0) { alert("Coefficient 'a' cannot be zero in a quadratic equation."); return; } var disc = (b * b) – (4 * a * c); valDisc.innerHTML = disc.toFixed(4); resArea.style.display = 'block'; if (disc > 0) { var x1 = (-b + Math.sqrt(disc)) / (2 * a); var x2 = (-b – Math.sqrt(disc)) / (2 * a); valX1.innerHTML = x1.toFixed(4); valX2.innerHTML = x2.toFixed(4); msgType.innerHTML = "Two distinct real roots found."; } else if (disc === 0) { var x = -b / (2 * a); valX1.innerHTML = x.toFixed(4); valX2.innerHTML = x.toFixed(4); msgType.innerHTML = "One repeated real root found."; } else { var realPart = (-b / (2 * a)).toFixed(4); var imagPart = (Math.sqrt(-disc) / (2 * a)).toFixed(4); valX1.innerHTML = realPart + " + " + imagPart + "i"; valX2.innerHTML = realPart + " – " + imagPart + "i"; msgType.innerHTML = "Two complex (imaginary) roots found."; } }

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