Find the Roots of a Quadratic Equation in C

Exercise:

Write a C Program to find the roots of a quadratic equation.

Click Here to View the Solution!
#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;
} 
Click Here to View the Output!
Enter coefficients a, b and c: 6 12 2  
root1 = -0.18 and root2 = -1.82 
Click Here to View the Explanation!
  • This program is used to determine the roots of a quadratic equation.
  • The program requests the user to enter three coefficients a, b, c and store them in the double type variables a, b and c using the scanf() function.
  • The determinant is then calculated using the formula (b*b – 4*a*c).
  • If…else if statements are used to determine the nature of the roots.
  • If the discriminant is greater than 0 the roots are real and different and are calculated using the formulas (-b + sqrt(discriminant)) / (2 * a) and (-b – sqrt(discriminant)) / (2 * a) and are printed, where sqrt is a function for calculating the square root of a number.
  • If the discriminant is equal to 0, the roots are real and equal and are calculated using the same formula (-b / (2 * a)) and are printed.
  • Else, the discriminant would be less than 0, the roots would not be real and the real and imaginary parts of the roots are calculated using the formulas (-b / (2 * a)) and (sqrt(-discriminant) / (2 * a)) and are printed.
  • The return 0 statement is used to exit the program execution.
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