Kotlin Program to Find all Roots of a Quadratic Equation

In this article, we will understand how to calculate the roots of a quadratic equation in Kotlin. A quadratic equation is an algebraic expression of the second degree or in other words, it has two results i.e., real number and an imaginary number.

Below is a demonstration of the same

Suppose our input is ?

a = 1, b = 2, c = 3

The desired output would be ?

The roots of the quadratic equation are
root1 = -1.00+1.41i
root2 = -1.00-1.41i

Algorithm

• Step 1 ? Start

• Step 2 ? Declare six values: inputA, inputB, inputC, root1, root2, myResult

• Step 3 ? Define the values

• Step 4 ? Compute ( inputB * inputB - 4.0 * inputA * inputC) and assign the result to myDeterminant

• Step 5 ? In a for loop, check if the value of myDeterminant variable is greater than 0, and if true, use quadric formula for root1 = (-inputB + Math.sqrt(myDeterminant)) / (2 * inputA) and for root2 = (-inputB - Math.sqrt(myDeterminant)) / (2 * inputA) to find the value, and assign it to a variable.

• Step 6 ? If the myDeterminant value is equal to 0, assign (-inputB / (2 * inputA)) to both root values.

• Step 7 ? If the myDeterminant value is less than 0, then compute val realPart = -inputB / (2 * inputA)

val imaginaryPart = Math.sqrt(-myDeterminant) / (2 * inputA)

• Step 8 ? Display the result

• Step 9 ? Stop

Example 1

In this example, we will find all the Roots of a Quadratic Equation. First, declare the input variables ?

val inputA = 1.0
val inputB = 2.0
val inputC = 3.0

Now, set the variable for roots and the result ?

val root1: Double
val root2: Double
val myResult: String

Calculate the Determinant using the formula ?

b² - 4ac

Apply the above formulae to get the Determinant ?

val myDeterminant = inputB * inputB - 4.0 * inputA * inputC

Use if?elseif?else to display all the roots of a Quadratic Equation ?

if (myDeterminant > 0) {
   root1 = (-inputB + Math.sqrt(myDeterminant)) / (2 * inputA)
   root2 = (-inputB - Math.sqrt(myDeterminant)) / (2 * inputA)
   
   myResult = "root1 = %.2f and root2 = %.2f".format(root1, root2)
}
else if (myDeterminant == 0.0) {
   root2 = -inputB / (2 * inputA)
   root1 = root2

   myResult = "root1 = root2 = %.2f;".format(root1)
}
else {
   val realPart = -inputB / (2 * inputA)
   val imaginaryPart = Math.sqrt(-myDeterminant) / (2 * inputA)

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

Let us now see the complete example ?

fun main() {

   val inputA = 1.0
   val inputB = 2.0
   val inputC = 3.0

   println("The input values are defined as $inputA, $inputB and $inputC ")

   val root1: Double
   val root2: Double
   val myResult: String
   val myDeterminant = inputB * inputB - 4.0 * inputA * inputC

   println("The roots of the quadratic equation are: ")
   
   if (myDeterminant > 0) {
      root1 = (-inputB + Math.sqrt(myDeterminant)) / (2 * inputA)
      root2 = (-inputB - Math.sqrt(myDeterminant)) / (2 * inputA)
      myResult = "root1 = %.2f and root2 = %.2f".format(root1, root2)
   }
   
   else if (myDeterminant == 0.0) {
      root2 = -inputB / (2 * inputA)
      root1 = root2
      myResult = "root1 = root2 = %.2f;".format(root1)
   }

   else {
      val realPart = -inputB / (2 * inputA)
      val imaginaryPart = Math.sqrt(-myDeterminant) / (2 * inputA)
      myResult = "root1 = %.2f+%.2fi and root2 = %.2f-%.2fi".format(realPart, imaginaryPart, realPart, imaginaryPart)
   }
   println(myResult)
}

Output

The input values are defined as 1.0, 2.0 and 3.0
The roots of the quadratic equation are:
root1 = -1.00+1.41i and root2 = -1.00-1.41i

Example 2

In this example, we will find all the Roots of a Quadratic Equation using a custom function ?

fun main() {
   val inputA = 1.0
   val inputB = 2.0
   val inputC = 3.0
   println("The input values are defined as $inputA, $inputB and $inputC ")
   getRoots(inputA, inputB, inputC)
}

fun getRoots(inputA: Double, inputB: Double, inputC: Double) {
   val root1: Double
   val root2: Double
   val myResult: String
   val myDeterminant = inputB * inputB - 4.0 * inputA * inputC
   println("The roots of the quadratic equation are: ")
   
   if (myDeterminant > 0) {
      root1 = (-inputB + Math.sqrt(myDeterminant)) / (2 * inputA)
      root2 = (-inputB - Math.sqrt(myDeterminant)) / (2 * inputA)
      myResult = "root1 = %.2f and root2 = %.2f".format(root1, root2)
   }

   else if (myDeterminant == 0.0) {
      root2 = -inputB / (2 * inputA)
      root1 = root2
      myResult = "root1 = root2 = %.2f;".format(root1)
   }

   else {
      val realPart = -inputB / (2 * inputA)
      val imaginaryPart = Math.sqrt(-myDeterminant) / (2 * inputA)
      myResult = "root1 = %.2f+%.2fi and root2 = %.2f-%.2fi".format(realPart, imaginaryPart, realPart, imaginaryPart)
   }
   println(myResult)
}

Output

The input values are defined as 1.0, 2.0 and 3.0
The roots of the quadratic equation are:
root1 = -1.00+1.41i and root2 = -1.00-1.41i