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

Question

10.3k 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 | 10.3k 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;
}