Algorithms Blog C

Program to find Roots of a Quadratic Equation

In this post You’ll be learning how to write a program for finding out the roots of a quadratic equation in various programming language.

Standard form a quadratic equation is

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

Shridhara’s Formula

According to Shridhara’s formula

b2-4ac is the value of the term discriminant in quadratic equation.

Value of discriminant defines nature of roots.

  1. If value of discriminant is greater than 0 then equation has real roots.
  2. Discriminant is 0 then equation has equal and real roots.
  3. If the discriminant is less than 0, the roots are complex and different.

C Program to Find Roots of a Quadratic Equation

#include <math.h>
#include <stdio.h>
int main() {
    double a, b, c, discriminant, root1, root2, realPart, imagPart;
    printf("Enter coefficients a, b and c: ");
    scanf("%lf %lf %lf", &a, &b, &c);

    discriminant = b * b - 4 * a * c;

    // condition for real and different roots
    if (discriminant > 0) {
        root1 = (-b + sqrt(discriminant)) / (2 * a);
        root2 = (-b - sqrt(discriminant)) / (2 * a);
        printf("root1 = %.2lf and root2 = %.2lf", root1, root2);

    // condition for real and equal roots
    else if (discriminant == 0) {
        root1 = root2 = -b / (2 * a);
        printf("root1 = root2 = %.2lf;", root1);

    // if roots are not real
    else {
        realPart = -b / (2 * a);
        imagPart = sqrt(-discriminant) / (2 * a);
        printf("root1 = %.2lf+%.2lfi and root2 = %.2f-%.2fi", realPart, imagPart, realPart, imagPart);

    return 0;


Enter coefficients a, b and c: 2.3
root1 = -0.87+1.30i and root2 = -0.87-1.30i

In this program, the sqrt() library function is used to find the square root of a number. To learn more, visit: sqrt() function. Read more about programming here

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