while loops...a problem with my simple code?

I think there may be a problem with my usage of brackets below.

Any ideas on this simple program to find roots of quadratic equation?

many thanks!

include Code:

#include <stdio.h>

#include <stdlib.h>

#include <math.h>

int main()

{

char answer;

int a,b,c;

float single_root, root_part1, root_part2;//declaring function variables these

//being different elements of the

//quadratic formula

float root1, root2;

int is_complex;

do

printf("Enter coeficients a b c: ");

scanf("%f %f %f", &a, &b, &c);

is_complex = 0; //(is_complex) function = 0 if a=0

if (a==0)

{

single_root=-1.0*c/b;//stating variables

}

else

{

root_part1 = -1.0*b/(2.0*a); //stating variables

root_part2= b*b-4.0*a*c;

if (root_part2<0.0)

{

is_complex = 1;

root_part2= -1.0*root_part2;//remember this is not equal to,

//this is a directive

}

root_part2=sqrt(root_part2)/(2.0*a);

}

if(a==0.0)

{

Printf("single_root = %f\n ", single_root);//single root case

}

else if (is_complex==1)

{

printf("root 1 = %.2f+%.2f i\n", root_part1, root_part2);

printf("root 1 = %.2f-%.2f i\n", root_part1, root_part2);

}

else

{

root1= root_part1+root_part2;

root2= root_part1-root_part2;

printf("root1 = %.2f", root1);

printf("root2 = %.2f", root2);

}

{

printf("enter next set of coefficients (y/n): ");

scanf(" %c", &answer);

}

while (answer != 'n' && answer != 'N');

scanf("d\n");

exit(0);

}