If a is 0 , then equation is not quadratic , but linear
if ( a == 0 ) { cout << " Invalid " ; return ; } int d = b * b - 4 * a * c ; double sqrt_val = sqrt ( abs ( d ) ) ; if ( d > 0 ) { cout << " Roots ▁ are ▁ real ▁ and ▁ different ▁ STRNEWLINE " ; cout << ( double ) ( - b + sqrt_val ) / ( 2 * a ) << " STRNEWLINE " << ( double ) ( - b - sqrt_val ) / ( 2 * a ) ; } else if ( d == 0 ) { cout << " Roots ▁ are ▁ real ▁ and ▁ same ▁ STRNEWLINE " ; cout << - ( double ) b / ( 2 * a ) ; }