Floating Point: Square root of negative number

Lieta tāda, ka palaižot programmu, ievadot jebkādu skaitli (pozitīvu/negatīvu) man izmet tādu erroru - Floating Point: square root of negative number. Saprotu, ko tas nozīmē, bet savā kodā nevaru atrast kļūdu (t.i. nesaprotu, ko vajag izmainīt, lai programma ietu).

šeit būs kods:

# include <stdio.h>
# include <conio.h>
# include <math.h>

void main(void)
{float a,b,x,y;

printf("enter a value of x \n");
scanf("%f", &x);

a = pow(((pow(x,3)+pow(136,1/7))/0,00034),1/5);
b = (log(2))*exp(-4*(atan(3+2*sqrt(x))-atan(sqrt(2)/x)));

if (2*fabs(a)<=9*b)

y = (exp(-a)+exp(-b))/(2*fabs(a)+3*fabs(b));
else
y = (a-b)/(3*pow(a,2)+4*pow(b,2));

printf("x=%f; a=%f, b=%f, y=%f\n",x,a,b,y);
getch() ;
}