10-26 Exercise 3: Find roots of a quadratic equation

Question

13.7k views

Write a program to find roots of a quadratic equation

A quadratic equation is a second order equation having a single variable. Any quadratic equation can be represented as where a, b and c are constants ( a can't be 0) and x is unknown variable.

寫一個找二次方程的求根程式

For Example

is a quadratic equation where a, b and c are 2, 5 and 3 respectively.

To calculate the roots of quadratic equation we can use below formula. There are two solutions of a quadratic equation.

使用下列公式:

x = (-b + sqrt(D))/(2*a)
x = (-b - sqrt(D))/(2*a)

where, D = (b*b-4*a*c) is Discriminant (判別式), which differentiate the nature of the roots of quadratic equation.

For the complex result (複數根):

realPart = -b/(2*a);
imaginaryPart =sqrt(-D)/(2*a);

Note: We have used sqrt() function to find square root which is in math.h library.

Example input 1:

1 2 1

Example output 1:

Roots of 1.00x^2 + 2.00x + 1.00 = 0 are real and same
x1 = x2 = -1.00

Example input 2:

1 -3 2

Example output 2:

Roots of 1.00x^2 + -3.00x + 2.00 = 0 are real and different
x1 = 2.00
x2 = 1.00

Example input 3:

1 2 2

Example output 3:

Roots of 1.00x^2 + 2.00x + 2.00 = 0 are complex and different
x1 = -1.00+1.00i
x2 = -1.00-1.00i

[Exercise] Coding (C) - asked Oct 26, 2017 in Chapter 5: Selection Statements by semicolon (5.2k points)
ID: 28934 - Available when: 2017-10-26 18:00 - Due to: Unlimited
reopened Oct 26, 2017 by thopd | 13.7k views

56 Answers

Page:

« prev
1
2
3
4
5
6
next »

112233 · Answer 1 · 2017-11-09 17:27:38

Hidden content!
#include  *  * **  *  *** 
#include   *  ** ** * * *

int main()
{
*  **   ** **            ** * a, b, c, determinant, x1,x2, realPart, *******  *


 **  * * **** ****    ****   *  **** %lf  ** **  * *   * &b, &c);


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

*  *  ***** *****  * condition for real and different roots


 **  *  *  * *  *  *** **  *   * ** for real and equal roots
**   *  *   ** *  *       **   *   (determinant == 0)
* *  * *  ** * ***** * **   * *
 * *** ****** *    **  ** *  **   *  *    **     *** ***   = x2 = -b/(2*a);
* *  * *       **  **** ** *** * ***  **** *  **  * ******        *** ** * of %.2fx^2 + %.2fx + %.2f = 0 are real and *  **  a,b,c);
      * **  *  ** *    ***     * * * *** * * *    ** **     = x2 = **   **** x1);
** **    *   *  *  ***  * * 

*  **   *  **    ** *  ** * **** * *   if  **  *  * * > 0)
* *  *    * * *   ** * ** ****
** ***  ***  * *    * ** * sqrt() function returns square root
 *** **  **   * * *  ** ** *  *    *   *     ***  **  =   *  *   ****      **  *
  **** *  ***    ***    *** ******   ** ** ** *   *   =  ***  * **** ** * ***

**** * ***  ****  *   **  **   ** *****    *******      **  ***  ** of %.2fx^2 + %.2fx + %.2f = 0 are real and *  * * ** ** *** ** 
* * * ***  **  **  **  **** ***  **  * ***  * * **  ** *** ****  ********  =      * * *   x1);
**  *  ****    *****  ******* **       * *  *** * *  *  * * ***** *  ** =  **  *   x2);
*  ****** * **     *  ***** * if roots are not real
 **     ** ** **    **  * * *
 * ** **    ***  **  *
   ** **** ***    ***  ***    *  **** *    *  **** **  = -b/(2*a);
**  ** *****   *   *  ** ***** ********* *** **   **  *   **** *   * =      *  * ***
   **  **********  *  **  ***    * **  *  ** *    ****  ** *** * **  * of %.2fx^2 + %.2fx + %.2f = 0 are complex and * *    *   ** * * a,b,c);
*** ** ** **  *  **  *  * * ***  * ***** *  *          *** **  **** ** = * **    ** ***   realPart,     * **  *
****       *******  * *  ** ** *    **  **  ***    *** = * ***  * **   realPart, **  ** 
    **     ***   * * ** **

  *     * **** *** *** ****  * 0;
}

answered Nov 9, 2017 by 112233 (-167 points)

112233 · Answer 2 · 2017-11-09 17:17:35

Hidden content!
#include         **   ***  
#include  *      ****  

int main()
{
 *    **   *  ** **   *   ***  * * a, b, c, determinant, x1,x2, realPart,  **** ***  


** * ***** * ***** * ***   **** *  **   * %lf  * **** *** *  *    &b, &c);


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

      **   **  *****    * * ** **  condition for real and different roots
***  *  **  * * **  *   ** *** (determinant > 0)
***  **   **    * *  * *
   *      * *  *   *****    ***  sqrt() function returns square root
  * * * * *    * **  ***  *  **   ** *** ** *   *  *  =  * * *  ** *  * * 
 **     *   ***  * ****** ** ** **       * * ** ** * *  *   = *   **  * *** **** 

 ****  *      ***  *** ** *    ***  * *  **  *     *********   of %.2fx^2 + %.2fx + %.2f = 0 are real and ***** *  * **    *    *
*    * * *  * *   *** *    *  ***** ***   * *  *  ***  * ****** * =   ***  ***  x1);
    *   ****   * *****  *       **  * *  *** *** *** **   ******* = **** * * x2);
  ***  ** ***  *     **  *  

*  *** ** ***   *  *  ****  *   *   for real and equal roots
** *  *   ***** * ** **    *   **  if (determinant == 0)
  *   *  *    * ***
 *  *  ** *  * * ** *    **  *     * ** ***      * **  *   = x2 = -b/(2*a);
 *   **  *** ****** * *  ** ***   **    ** **   ** **** ** **  *** **  *   of %.2fx^2 + %.2fx + %.2f = 0 are real and  ** *     *   a,b,c);
  **** **** *** *** *   *     * * ** * ** ** *  * **** *    *** = x2 = * * *    * x1);
* ***** *****  **   **   *****

    * **  *    **  * **** * *** if roots are not real
 *   *  ** ***  ***** *   ** ** **
*** * *  *********  * *   *
 ***  **   **         *      **     ***** ****  *  *  = -b/(2*a);
 **** ** ***  **      * *  *****   *  ** *** ***     * **** =   **   *  *  * 
       **** * **             *    *   *   ***  ***   *  ****   ***   of %.2fx^2 + %.2fx + %.2f = 0 are complex and *** *  ***** ** a,b,c);
 *** *  *  *** * * ***    ** * *** *  ***** * ******  =  ** *  * * ****** realPart,  *** **    *
*  * * ** * *  *   *** * * *  * ** ***   ***** ****    **   *** **   =   ** *  *  *    *  realPart, ******** 
***** *** *** ****  **   *

*  *  **  ** *     ** * ***  *  * 0;
}

answered Nov 9, 2017 by 112233 (-167 points)

garrylin2 · Answer 3 · 2017-11-02 19:54:55

Hidden content!
***** *** ** * *  *  
  *  *  ** * *      
int main(void)
{
 ***  * ** ** ***** **** *  a,b,c,d;
* *  *    *     *   ** *  *     *****  %f    * ** ** *    * ****  **  * ** **
** **  ***  **      * **** * * * ** * 
   **** **  * *  *  *   * *** *   * *  * 
    **  ** * **  *    ** *     * *   *  * * * * ** * ***** * * **     of %.2fx^2 + %.2fx + %.2f = 0 are real and  ** * * = %.2f\nx2 =  *  *** * ** *  +   *** *      -   *   *   * 
 *  * *      *  **    ** **  
*** * *  ** *** * *   **  * *   (d==0){
*   * ** *     ** ** *** * ****  *   **  ** ** **  * *****      ** * of %.2fx^2 + %.2fx + %.2f = 0 are real and same\nx1 = x2 =   ** *  **  *      +  * * ** ** *
 * ***** ** **** *  *** *    *
  *** ****     ***  *    * **   (d<0) {
   ***  *  **  *      * * * ** *** *  ***   ***   ** *    *  * * **  of %.2fx^2 + %.2fx + %.2f = 0 are complex and       *  = *  ** * *  =  ***    **  *   ******     ** *** ** ****   *    **   * 
*     * * ***    * *****  *
}

answered Nov 2, 2017 by garrylin2 (-204 points)

garrylin2 · Answer 4 · 2017-11-02 19:53:31

Hidden content!
**** ***   ** * *
* *     *   ***  * * * 
int main(void)
{
 ** *  * **  * *  *   * *  **  a,b,c,d;
  * * **  * ** *   ** *   *** ***  *** *  *  ** %f   **  *** ** *** *  *   * ***** **
**   ** *** *   *  ** ** ** ** * *** *
* * *  *****   *  *  *    (d>0){
**   **   ** *  ** *   * ****  * * * ***  *  *     ** *   of %.2fx^2 + %.2fx + %.2f = 0 are real and **** * ** = %.2f\nx2 = * ** * **** ** ** + *  *  * - *  *  *   *
*    **  *         * **  *
 ** ***  * *   *    *    * **  (d==0){
  * * * **** ** *** ** *   *** * ****  * ** *   * *  * *  *****   **    of %.2fx^2 + %.2fx + %.2f = 0 are real and same\nx1 = x2 = * ***  ** * *  ***  * + **  * ** 
*** * * ****  ** * * ** ***** 
   ***** ***   * ** **   *  **   ** {
  * *      * **  ** ******** **     *  *  * * *  *   ***** * * ** ******   of %.2fx^2 + %.2fx + %.2f = 0 are complex and ****   *  = ** ***  =    ** * ***    **** * * *   *  **   * * ** * **  *** 
*** * *  ** *   ** ********
}

answered Nov 2, 2017 by garrylin2 (-204 points)

rick · Answer 5 · 2017-11-02 19:34:07

prog.c: In function 'main':
prog.c:5:5: warning: implicit declaration of function 'scanf' [-Wimplicit-function-declaration]
     scanf("%f %f %f",&a,&b,&c);
     ^~~~~
prog.c:5:5: warning: incompatible implicit declaration of built-in function 'scanf'
prog.c:5:5: note: include '<stdio.h>' or provide a declaration of 'scanf'
prog.c:13:9: warning: implicit declaration of function 'printf' [-Wimplicit-function-declaration]
         printf("Roots of %.2fx^2 + %.2fx + %.2f = 0 are real and different\nx1=%.2f\nx2=%.2f\n",a,b,c,x1,x2);
         ^~~~~~
prog.c:13:9: warning: incompatible implicit declaration of built-in function 'printf'
prog.c:13:9: note: include '<stdio.h>' or provide a declaration of 'printf'
prog.c:17:9: warning: incompatible implicit declaration of built-in function 'printf'
         printf("Roots of %.2fx^2 + %.2fx + %.2f = 0 are real and same\nx1 = x2 = %.2f",a,b,c,x1);
         ^~~~~~
prog.c:17:9: note: include '<stdio.h>' or provide a declaration of 'printf'
prog.c:21:9: warning: incompatible implicit declaration of built-in function 'printf'
         printf("Roots of %.2fx^2 + %.2fx + %.2f = 0 are complex and different\nx1 = %.2f+%.2fi\nx2 = %.2f-%.2fi",a,b,c,x3,x4,x3,x4);
         ^~~~~~
prog.c:21:9: note: include '<stdio.h>' or provide a declaration of 'printf'

rick · Answer 6 · 2017-11-02 19:28:09

Hidden content!
#include<stdio.h>
#include<math.h>
int main()
{
* * *    * * *  *****  ** *****  a,b,c,d,x1,x2,x3,x4;
* *******  *  ** ** *  **   ***  * %f *     ** ***    ******  **  
 **   **  * *  * * *  **  **  * *** *
*   ****    * ** *** ** *    * **    ** *** 
 ** *  ** ***  *  ******* ***     ** * ** *
 ** *   ***  *****  *******  **   **
*** **   *** **    **  * ****      ** *
*  ** *  *** ****  *   *  ***  *     *** ***** ** * *
** * *** **  **** *  * * * 
* * * * *  *      *  ** *  * *  * *  **      **  **  *** **  ** *  of %.2fx^2 + %.2fx + %.2f = 0 are real and * **  * ** **  *** *        * *
***** *      *** *****  *  **** **
* * * ****** ** *   ** *  *  ***   *** *** *  ****
    * *  * **   ** * **    * * **  *
*  * * * ** **** * *     *  *  **** *   * ****** *  *  * ****  * *  **   of %.2fx^2 + %.2fx + %.2f = 0 are real and same\nx1 = x2 = %.2f",a,b,c,x1);
* ****       ** * *    ***
* ***** *** *  *********  ** * **      ** ***  ** * *   *
*  **  * *   * ****  * *   
 ******** **** * ******* ****  *     ***  **********  **  *    of %.2fx^2 + %.2fx + %.2f = 0 are complex and different\nx1 = %.2f + %.2fi\nx2 = %.2f - *  * * *  **  * ** * 
  *  **** *   * ****   
**  **  *  *** ** ** *    *** *** **     0;
}