error C2181: illegal else without matching if

#include #include void main() { double a=1,b=-5,c=6,d,x1,x2; if(b*b-4*a*c>=0) { //加括号 d= sqrt(b*b-4*a*c); x1= (-b+d)/(2*a); x2= (-b-d)/(2*a); printf("x1=%.3f,x2=%.3f\n",x1,x2); } //