Quad equation using fuctions problem

This is a discussion on Quad equation using fuctions problem within the C++ Programming forums, part of the General Programming Boards category; Code: #include <iostream> using namespace std; void quadraticequation(float a, float b, float c); int main() { int a,b,c; cout <<"a"<< ...

  1. #1
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    Quad equation using fuctions problem

    Code:
    #include <iostream>
    using namespace std;
    void quadraticequation(float a, float b, float c);
    
    int main()
    {
    	int a,b,c;
    	
    	cout <<"a"<< endl;
    	cin>>a;
    	cout<<"b"<<endl;
    	cin>>b;
    	cout<<"c"<<endl;
    	cin>>c;
    	quadraticequation(a,b,c);
    	
    }
    
    
    	void quadraticequation(float a, float b, float c)
    {
    	if (((b*b)-4*a*c)<0)
    		{
    		cout<<"No real solution"<<endl;
    		}
    	
    	else if (((b*b)-4*a*c)=0 )
    		{
    		cout<<"Answer is"<<-b/2*a;
    		}
    	
    	 else if (((b*b)-4*a*c)>0)
    		 {
    		  cout<<"X1 ="<< -b+sqrt((b*b)-4*a*c)/2*a;
    		  
    		  cout<<"X2 ="<< -b-sqrt((b*b)-4*a*c)/2*a;
    		  }
    	
    	
    	
    }
    In the above code I'm to write out a function that solves a quadratic equation. I have one error that comes up but I dont know how to stop it because it seems okay to me(the beginner ). Does anyone know where I went wrong??

  2. #2
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    903
    Try to always tell us what the errors are when you get them. It seems to me the error comes from the fact that you have mistaken '==' for '='. It's in your first 'else if' statement.

  3. #3
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    Well, mathematically you should have
    Code:
    	  cout<<"X1 ="<< (-b+sqrt((b*b)-4*a*c))/(2*a);
    	  cout<<"X2 ="<< (-b-sqrt((b*b)-4*a*c))/(2*a);
    You could also save some typing by defining a variable for b*b-4*a*c.

    Edit: And also
    Code:
    		cout<<"Answer is"<<-b/(2*a);
    Last edited by robatino; 12-07-2006 at 10:09 AM.

  4. #4
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    Code:
    #include <math.h>
    #include <iostream>
    using namespace std;
    void quadraticequation(float a, float b, float c);
    
    int main()
    {
    	int a,b,c;
    	
    	cout <<"a"<< endl;
    	cin>>a;
    	cout<<"b"<<endl;
    	cin>>b;
    	cout<<"c"<<endl;
    	cin>>c;
    	quadraticequation(a,b,c);
    	
    }
    
    
    	void quadraticequation(float a, float b, float c)
    {
    	if (((b*b)-4*a*c)<0)
    		{
    		cout<<"No real solution"<<endl;
    		}
    	
    	else if (((b*b)-4*a*c)==0 )
    		{
    		cout<<"Answer is"<<-b/(2*a);
    		}
    	
    	 else if (((b*b)-4*a*c)>0)
    		 {
    		  cout<<"X1 ="<< (-b+sqrt((b*b)-4*a*c))/2*a;
    		  
    		  cout<<"X2 ="<< (-b-sqrt((b*b)-4*a*c))/2*a;
    		  }
    	
    	
    }

  5. #5
    CSharpener vart's Avatar
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    there are two more places with /2*a that should be fixed
    The first 90% of a project takes 90% of the time,
    the last 10% takes the other 90% of the time.

  6. #6
    Registered User
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    Mar 2006
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    Thanks guys, It works now. I really appreciate the help, I have an exam in this Wednesday and up till today I was clueless, still am but I think I know the basics.

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