# Kotlin Program to Find Roots of Quadratic Equation

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In this post, we will go through Kotlin program to find roots of quadratic equation

###### What is a quadratic equation?

In algebra, a quadratic equation is any equation that can be expressed in standard form as
ax2 + bx + c = 0

Where, a, b and c are real numbers and a is not 0.
x is variable (Either real or complex value) for which this equation is satisfied.

We can find roots of equation (value of x that satisfy equation) using formula –

x = (-b ± √b2 -4ac) / 2a

It means,

First root is
x = (-b + √b2 -4ac) / 2a

and,

Second root is
x = (-b – √b2 -4ac) / 2a

Here, b2 – 4ac is called determinant that decides whether roots are real or imaginary (or complex). If

• determinant > 0: Roots are real and different
• determinant == 0: Roots are real and same
• determinant < 0: Roots are imaginary (or, complex) and different

## 1. Kotlin Program to Find Roots of Quadratic Equation

Now, let’s see program in Kotlin that finds roots of the quadratic equation.

```import java.util.*
import kotlin.math.sqrt

fun main() {

println("To form quadratic equation a * x * x + b * x + c = 0")

println("Enter a:")

println("Enter b:")

println("Enter c:")

val d: Double = (b * b) - (4 * a * c)       // This is determinant that decides whether roots are real or imaginary

when {
(d > 0) -> {
val firstRoot = (-b + sqrt(d)) / ( 2 * a)
val secondRoot = (-b - sqrt(d)) / ( 2 * a)

val output = "Roots of equation a * x * x + b * x + c = 0 => x = %.2f and x = %.2f"
.format(firstRoot, secondRoot)
println(output)
}
(d == 0.0) -> {
val firstRoot = -b / ( 2 * a)

val output = "Roots of equation a * x * x + b * x + c = 0 => x = %.2f and x = %.2f"
.format(firstRoot, firstRoot)
println(output)
}
else -> {
val realPart = -b / ( 2 * a)
val imaginaryPart = sqrt(-d) / (2 * a)

val output =
"Roots of equation a * x * x + b * x + c = 0 => x = (%.2f + %.2fi) and x = (%.2f - %.2fi)"
.format(realPart, imaginaryPart, realPart, imaginaryPart)
println(output)
}
}

}
```

When you run the program, output will be

```To form quadratic equation a * x * x + b * x + c = 0
Enter a:
1
Enter b:
0
Enter c:
-1
Roots of equation a * x * x + b * x + c = 0 => x = 1.00 and x = -1.00
```

Here, we have created an object of Scanner. Scanner takes an argument which says where to take input from.
System.`in` means take input from standard input – Keyboard.

read.nextDouble() means read anything (i.e. Double value) entered by user before space or line break from standard input – Keyboard.

Input read by scanner is then stored in variable year

At first, we are taking value of a, b, and c from user to form quadratic equation.

Then, we find value of determinant and store it in variable d

Then, as per value of determinant we find the roots of equation.

In all process we are keeping in mind the formula to find roots of equation.

x = (-b ± √b2 -4ac) / 2a

Finally, we print result value using println() method.

Thus, we went through Kotlin Program to Find Roots of Quadratic Equation.