Support Forums - Need help with this little program

I am beginner to c++, I want to make a program for Quadratic formula, only the positive part, but I can't make it.. I am trying this one

quadratic formula:
http://www.regentsprep.org/Regents/math/...adLe21.gif

Code:
#include<math.h>

#include<conio.h>

#include<stdio.h>

void main()

{

int a,b,c,s; float x, sq;

printf("\n Enter Values For a, b & c: ");

scanf("%d %d %d",&a,&b,&c);

s=b*b-1*4*a*c;

sq=pow(s,1/2);

x=(-1*b+s)/2*a;

printf("\n Positive solution of given quadratic equation is: %f",x);

getch();

}

please do corrections in it and help me

First off, what compiler do you use? printf() is old.

(01-17-2012, 04:36 AM)AceInfinity Wrote: [ -> ]First off, what compiler do you use? printf() is old.

I myself was using cin and cout but in our text book, they have used printf()

I am using Borland C++

Either way your equations are wrong, remember that order of operation comes into play, so USE BRACKETS where ever applicable to make sure that certain numbers get calculated first over others:

This is wrong anyway:

Code:
s=(b*b)-1*4*a*c;

where does the -1 come in? and
-4ac != -1*4*a*c

that would do:
= -4
= -4a
= c(-4a)

(01-17-2012, 04:22 PM)AceInfinity Wrote: [ -> ]Either way your equations are wrong, remember that order of operation comes into play, so USE BRACKETS where ever applicable to make sure that certain numbers get calculated first over others:

This is wrong anyway:

Code:
s=(b*b)-1*4*a*c;

where does the -1 come in? and
-4ac != -1*4*a*c

that would do:
= -4
= -4a
= c(-4a)

Hmm, there I am wrong, C++ does not support MINUS sign with a VARIABLE, I had this in mind and put it with a number too, but that does not matter anything. The problem is with SQUARE ROOT of Negative number...

You don't know about the square root methods in C++ or you're just having issues with it in any updated code so far?

What are you talking about C++ doesn't support Minus sign with a variable though??? Huh

Make sure your variable definitions have the "signed" attribute... and not "unsigned"

Edit: I may not be able to help with the equation, but I can help you with the coding if I know what you want to do. Been a while since I used that equation for anything, so I don't quite understand how it's used. But I can tell you how to get certain variables from that equation in code.

Hmm try this line instead of all the clutter you've got going on, i've put the formula all into one line:

Code:
x = (-b + sqrt(pow(b, 2) - (4 * a * c))) / (2 * a);

pow from math.h takes a double as input as well, not int.

Can't test as I have no idea of what kind of valid numbers would go into the equation however. You're last bit of the equation seems to have been right, just not sure where that 1 came in when you had it in your code... If it's not working, just reply with what happens at runtime with this. Or provide me with some valid numbers that can be used for this equation that I can fool around with. Smile

(01-18-2012, 08:53 AM)AceInfinity Wrote: [ -> ]You don't know about the square root methods in C++ or you're just having issues with it in any updated code so far?

What are you talking about C++ doesn't support Minus sign with a variable though???

Make sure your variable definitions have the "signed" attribute... and not "unsigned"

Edit: I may not be able to help with the equation, but I can help you with the coding if I know what you want to do. Been a while since I used that equation for anything, so I don't quite understand how it's used. But I can tell you how to get certain variables from that equation in code.
Hmm try this line instead of all the clutter you've got going on, i've put the formula all into one line:

Code:
x = (-b + sqrt(pow(b, 2) - (4 * a * c))) / (2 * a);

pow from math.h takes a double as input as well, not int.

Can't test as I have no idea of what kind of valid numbers would go into the equation however. You're last bit of the equation seems to have been right, just not sure where that 1 came in when you had it in your code... If it's not working, just reply with what happens at runtime with this. Or provide me with some valid numbers that can be used for this equation that I can fool around with.

Actually, I used the one line code that you have quoted but was the same error.
I now realize that the problem is not in code, it is in the combination of number I input to the program

Thanks for your brilliant time that you gave me

(01-21-2012, 08:30 AM)Clones Wrote: [ -> ]Actually, I used the one line code that you have quoted but was the same error.
I now realize that the problem is not in code, it is in the combination of number I input to the program

Thanks for your brilliant time that you gave me

Hmm, if I was a quadratic equation formula expert i'd be able to help you further haha, sorry about that friend Smile

I recognize the equation, but it's been some time since I last used it.

(01-21-2012, 08:39 AM)AceInfinity Wrote: [ -> ]Hmm, if I was a quadratic equation formula expert i'd be able to help you further haha, sorry about that friend

I recognize the equation, but it's been some time since I last used it.

you helped alot.. No problem