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

Question

9.1k 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 | 9.1k 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;
}