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

Question

14.8k 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 | 14.8k 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;
}