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

Question

15k 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 | 15k 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;
}