Quadratic Equation

[grider67]

I get a C4700 with a, b, c uninitialized local variable for Line 16.
What am I doing wrong?

//Write a program that prompts the user to input the value of a
//(the coefficient of x squared), b (the coefficient of x),
//and c (the constant term) and outputs the type of roots of the equation.
//Furthermore, if b squared - 4ac greater than/equal 0, the program
//should output the roots of the quadratic equation.


#include <iostream>
#include <cmath>
using namespace std;

int main()

{
	float a, b, c;
	float discriminant = (pow (b, 2) - 4 * a * c);
	float positive = (((-b) + sqrt(discriminant)) / (2 * a));
	float negative = (((-b) - sqrt(discriminant)) / (2 * a));

	cout << "Enter a:"; //The coefficient of x squared
	cin >> a;
	cout << "Enter b:"; //The coefficient of x
	cin >> b;
	cout << "Enter c:"; //The constant term
	cin >> c;

	cout << "The discriminant is " << endl;
	cout << discriminant << endl;

	if (discriminant == 0)
	{
		cout << "The equation are single root." << endl;
	}
	else if (discriminant < 0)
	{
		cout << "The equation are two complex root." << endl;
	}
	else
	{
		cout << "The equation are two real root." << endl;
	}

	return 0;
}

[jonnin]

this appears to be an error for uninitialized variables. which makes sense, you don't give a,b,c values until after you tried to do computations with them.

[Ganado]

This confuses some beginners. Note that variables in C++ are not really like the concept of a "variable" in math. They're similar, but in C++ you can't calculate "2 * x" symbolically, and then plug in the x afterwards. When "2 * x" is calculated, the value of x must already be known.

Basically, move your lines 16, 17, 18 to after the lines where you ask for input.