1>

program giai_phuong_trinh_bac_2;
uses crt;
var a, b, c, x1, x2, x, dt : real;
begin
clrscr;
write('nhap lan luot he so a, b, c :'); readln(a, b, c);
dt :=b*b - 4*a*c;
if dt >0 then
begin
writeln('phuong trinh co 2 nghiem phan biet la : ');
x1 := (-b + sqrt(dt))/(2*a);
x2 := (-b - sqrt(dt))/(2*a);
writeln('nghiem x1 =', x1:8:2);
writeln('nghiem x2 =', x2:8:2);
end
else
if dt = 0 Then
begin
x:=(-b/(2*a));
writeln('phương trinh co 1 nghiem kep la : ', x:8:2 );
x:=(-b/(2*a));
end
else
writeln(' Phương trinh vo nghiem');
readln;
end.

2>

program nam;
uses Crt;
var a, b : integer;
begin clrscr();
write('nhap thang :'); readln(a);
write('nhap nam :'); readln(b);
if (a=2) and (b mod 4 = 0) then writeln ('thang 2 nam', b,' co 30 ngay');
if(a=2) and (b mod 4 <> 0) then writeln('thang 2 nam ', b,' co 29 ngay');
if a = 1 then writeln('thang 1 nam', b,' co 31 ngay');
if a = 3 then writeln('thang 3 nam', b,' co 31 ngay');
if a = 4 then writeln('thang 4 nam', b,' co 30 ngay');
if a = 5 then writeln('thang 5 nam', b,' co 31 ngay');
if a = 6 then writeln('thang 6 nam', b,' co 30 ngay');
if a = 7 then writeln('thang 7 nam', b,' co 31 ngay');
if a = 8 then writeln('thang 8 nam', b,' co 31 ngay');
if a = 9 then writeln('thang 9 nam', b,' co 30 ngay');
if a = 10 then writeln('thang 10 nam', b,' co 31 ngay');
if a = 11 then writeln('thang 11 nam', b,' co 30 ngay');
if a = 12 then writeln('thang 12 nam', b,' co 31 ngay');
readln
end.

3>

program tam_giac;
uses crt;
var a, h, s : real;
begin
clrscr;
write('nhap do dai canh a :');readln(a);
write('nhap do dai chieu cao h :');readln(h);
s := 0.5*a*h;
writeln('dien tich cua tam giac la :', s:8:2);
readln
end.

4>

program tam_giac;
uses crt;
var a, b, c, p, s : real;
begin
clrscr;
write('nhap do dai canh a :');readln(a);
write('nhap do dai canh b :');readln(b);
write('nhap do dai canh c :');readln(c);

p := ( a+b+c)/2;

s := sqrt(p*(p-a)*(p-b)*(p-c));

writeln('dien tich cua tam giac la :', s:8:2);
readln
end.

1, vt ct giải phương trình bậc 2

Program GIAI_PHUONG_TRINH_BAC_HAI;
Uses crt;
Var a,b,c,d,x,x1,x2:real;
Begin
Writeln('GIAI PHUONG TRINH BAC II:');
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<0 then
Writeln('Phuong trinh vo nghiem')
Else
Begin
x1:= (-b+sqrt(d))/(2*a);
x2:= (-b-sqrt(d))/(2*a);
Write('Phuong trinh co hai nghiem: ‘);
Writeln(‘ x1=',x1:4:2,' va x2=',x2:4:2);
End;
End;
Readln;
End.