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

Question

13.3k 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 | 13.3k 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;
}