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)??

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>
...