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

Question

7.6k 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 | 7.6k 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;
}