Giải phương trình bậc 2 ax2 + bx + c = 0 pascal

Program GIAI_PHUONG_TRINH_BACII; Uses crt; Var a,b,c,d,x,x1,x2: real; Begin Clrscr; Writeln['GIAI PHUONG TRINH BAC II: ']; Writeln['-------------------------------------------']; Write['Nhap he so a=']; readln[a]; Write['Nhap he so b=']; readln[b]; Write['Nhap he so c=']; readln[c]; If a=0 then If b=0 then If c=0 then Writeln['Phuong trinh co vo so nghiem'] Else Writeln['Phuong trinh vo nghiem'] Else Writeln['Phuong trinh co mot nghiem: x=',-c/b: 4: 2] Else Begin D:=b*b-4*a*c; If D=0 then Writeln['Phuong trinh co nghiem kep: x=',-b/[2*a]: 4: 2] Else If D