Problem with mathematical function in program

[newbprogrammer]

I just started programming in c++ and i tried to explore and do programs on my own... So i wanted to do a program that would help me in my daily school work ... a program to solve quadratic equations.. I wrote the code correctly but errors are still detected and i have no idea why.. almost gave up and banged my head on the wall .. so i would really appreciate help.. This is the code so far..
[code=cpp]
#include <cmath>
#include <iostream>

using namespace std;

int main()
{
double x;
double y;
double z;

cout<<"Please enter the coeff of (x square):";
cin>> x;
cout<<"Please enter the coeff of (x):";
cin>> y;
cout<<"Please enter the number without the unknown (x):";
cin>> z;

double b = (((y * y) - (4 * x * z)));
double a = ((-y + (sqrt (b)) / (2 * x)));
double c = ((-y - (sqrt (b)) / (2 * x)));

cout<<"X = "<< a << "or" << c;
cin.ignore();
cin.get();
}[/code]
The answers i get arnt even close to the actual answers...

Please tell me what is wrong.. PLEASE PLEASE PLEASE
-------------------------------------------------------------------
This should help in understanding what i am trying to do.....

This program is supposed to solve equations like (3x^2 * -7x + 2)
so.. Using the general formula to solve this equation we take the coeff of x^2 to be "x", coeff of x to be "y" and coeff of number without unknown x to be "z".
Therefore x = 3
y = -7
z = 2
The equation to find x = ((-y) + sqrt((y^2) - (4*x*z))) / 2*x)
so... resulting to.. x = (7 + (sqrt (49 - 24)) / 6
and.. x = (7 + 5)/6
x = 2 //
As you can see.. in my code.. double b should = 25...

Any questions please ask.. i need help to solve this program.. I just really want to finish this program so please help

[vikasdev]

In the statement
[code=cpp]
double a=(.......) .check the parenthesis u hav given.it shud be
a=(-y+(sqrt(b)))/(2*x);[/code]
now it will give correct output....
and plz check that b(determinant)> =0,before proceeding further...

[newbprogrammer]

Thanks alot....it works now but if determinant is less then 0 how do i make the code say answer not valid or possible.. i just have to add (double b > 0)??

[Ganon11]

Have you looked at if statements? You might do something like:

[CODE=cpp]// Calculate value of b...
if (b < 0) {
// Answer is an imaginary number.
} else if (b == 0) {
// Only one real answer
} else {
// Two real answers.
}[/CODE]