Kotlin Program to Find all Roots of a Quadratic Equation

In this program, you'll learn to find all roots of a quadratic equation (depending upon the determinant) and print them using format() in Kotlin.

The standard form of a quadratic equation is:

ax2 + bx + c = 0, where
a, b and c are real numbers and
a ≠ 0

The term b2-4ac is known as the determinant of a quadratic equation. The determinant tells the nature of the roots.

  • If determinant is greater than 0, the roots are real and different.
  • If determinant is equal to 0, the roots are real and equal.
  • If determinant is less than 0, the roots are complex and different.

Example: Kotlin Program to Find Roots of a Quadratic Equation

fun main(args: Array<String>) {

    val a = 2.3
    val b = 4
    val c = 5.6
    val root1: Double
    val root2: Double
    val output: String

    val determinant = b * b - 4.0 * a * c

    // condition for real and different roots
    if (determinant > 0) {
        root1 = (-b + Math.sqrt(determinant)) / (2 * a)
        root2 = (-b - Math.sqrt(determinant)) / (2 * a)

        output = "root1 = %.2f and root2 = %.2f".format(root1, root2)
    }
    // Condition for real and equal roots
    else if (determinant == 0.0) {
        root2 = -b / (2 * a)
        root1 = root2

        output = "root1 = root2 = %.2f;".format(root1)
    }
    // If roots are not real
    else {
        val realPart = -b / (2 * a)
        val imaginaryPart = Math.sqrt(-determinant) / (2 * a)

        output = "root1 = %.2f+%.2fi and root2 = %.2f-%.2fi".format(realPart, imaginaryPart, realPart, imaginaryPart)
    }

    println(output)
}

When you run the program, the output will be:

root1 = -0.87+1.30i and root2 = -0.87-1.30i

In the above program, the coefficients a, b and c are set to 2.3, 4 and 5.6 respectively. Then, the determinant is calculated as b2 - 4ac.

Based on the value of determinant, the roots are calculated as given in the formula above. Notice we've used library function Math.sqrt() to calculate the square root of a number.

The output to be printed is then stored in a string variable output using the Kotlin's standard libary function format(). The output is then printed using println().


Here's the equivalent Java code of the above program: Java Program to Find all Roots of a Quadractic Equation