if (disc<o) printf( has not real roots\n i else p=-b/(20*a) g=sqrt(disc)/(2.0*ai x1=p+gi X2=p-gir printf( real roots: \nx1=%07.2f\n x2=%72f\n"rx1x2); return o 选择结构,用i语句实现的if (disc<0) printf(“has not real roots\n”); else { p=-b/(2.0*a); q=sqrt(disc)/(2.0*a); x1=p+q; x2=p-q; printf(“real roots:\nx1=%7.2f\n x2=%7.2f\n”,x1,x2); } return 0; } 选择结构，用if语句实现的