Help With Functions

Hello I am creating a program that solves the quadratic equation ax^2 + bx +c.

I have this program almost complete except the output of the equation in the function called display_quadratic. I need the program to display the variables a,b,c in the equation ax^2 + bx + c but I am having 2 problems. My first problem is that I cannot get the right addition and subtraction signs for the equation.

For instance, if the program had the values for a,b,c as 2,2,3

it will display 2x^2 2x 3

How can I get it to display 2x^2 + 2x + 3? or if it was negative like 2x^2 - 2x - 3?

My next question is how do I get to not display the coefficients that are 1?

I had an if-else statement but no matter what I created it would overlap with another statement and print out twice. Any help is appreciated and welcomed. Thank you.

Here is the code:

Code:

#include <stdio.h>
#include <stdlib.h>
#include <math.h>

void display_quadratic (float a, float b, float c);
float root1(float a, float b, float c);
float root2(float a, float b, float c);
float discriminant (float a, float b, float c);
float r1,r2;

int
main (void)
{
    float a,b,c;

    printf("This program solves the quadratic equation ax^2 + bx + c == 0.\n");
    printf("Enter a, b, and c:");
    scanf("%g%g%g", &a, &b, &c);
    printf("OK, the equation you're specifying is:");
    display_quadratic(a,b,c);
    printf(" == 0\n");

    r1 = root1(a,b,c);

    r2 = root2(a,b,c);

    printf("The roots of your equation are %g and %g, and the factorization is:\n ", r1,r2);

    display_quadratic(a,b,c);
    printf(" == ");

    if (r1 > 0)
    {
    printf("(x - %g)", r1);
    }
    else
    printf("(x + %g)", (r1 * -1));


    if (r2 > 0)
    {
    printf("(x - %g)", r2);
    }
    else
    printf("(x + %g)", (r2 * -1));
}


void display_quadratic (float a, float b, float c)
{

    if (a == 1){
        printf("x^2 ");}
    else printf("%gx^2 ", a);

    if (b == 1){
        printf("x ");}
    else printf("%gx ", b);

    printf("%g ", c);
}

float discriminant (float a, float b, float c)
{
    return (pow(b,2) - 4 * a * c);
}


float root1 (float a, float b, float c)
{
    float root1_calculator;

    root1_calculator = (-b + sqrt(discriminant(a,b,c)))/2 * a;

    return (root1_calculator);
}

float root2 (float a, float b, float c)
{
    float root2_calculator;

    root2_calculator =(-b - sqrt(discriminant(a,b,c)))/2 * a;

    return (root2_calculator);
}

Originally Posted by M_A_T_T

For instance, if the program had the values for a,b,c as 2,2,3

it will display 2x^2 2x 3

How can I get it to display 2x^2 + 2x + 3? or if it was negative like 2x^2 - 2x - 3?

The way you are doing it looks fine, except in your format you have 5 pieces, but your function is only handling 3:
2x^2
+
2x
+
3

You need an if/else to handle the + or minus sign. In other words, if b < 0, you need to print a minus. The same logic for coefficients of 1. If abs(b) == 1, you don't print the coefficient

Originally Posted by c99tutorial

The way you are doing it looks fine, except in your format you have 5 pieces, but your function is only handling 3:
2x^2
+
2x
+
3

You need an if/else to handle the + or minus sign. In other words, if b < 0, you need to print a minus. The same logic for coefficients of 1. If abs(b) == 1, you don't print the coefficient

So would it go like:

Code:

if (b < 0)
{
printf("-%gx +", b);
}
if (b > 0)
{
printf("%gx +", b);
}
if (abs (b) == 1)
{
printf("x");
}

What happens if lets say b is -3, then wouldn't it print --3?

Also when b = 1 or -1, how will it know when to print the + or - sign with the abs(b) == 1?

This was the situation I was getting stuck on.