program baitap;
uses crt;
var cv,s,a,b:integer;
begin
clrscr; 
a := 12;
b := 8;
cv := (a+b)*2;
s := a*b;
writeln('Chu vi HCN = ',cv);
writeln('Dien tich HCN = ',s);
readln;

cảm ơn ạ

Bài 3:

#include <bits/stdc++.h>

using namespace std;

double a,b;

int main()

{

cin>>a>>b;

cout<<fixed<<setprecision(2)<<a*b;

return 0;

}

3: 

#include <bits/stdc++.h>

using namespace std;

double a,b;

int main()

{

cin>>a>>b;

cout<<fixed<<setprecision(2)<<a*b;

return 0;

}

#include <bits/stdc++.h>

using namespace std;

long long a,b,dem,i;

int main()

{

cin>>a>>b;

dem=0;

for (i=a; i<=b; i++)

if ((i%2==1) and (i%3==0)) dem++;

cout<<dem;

return 0;

}

í B nhé

uses crt;

var xa,ya,xb,yb,xc,yc,p,s,ab,bc,ac:real;

begin

clrscr;

readln(xa,ya,xb,yb,xc,yc);

ab:=sqrt(sqr(xa-xb)+sqr(ya-yb));

ac:=sqrt(sqr(xa-xc)+sqr(ya-yc));

bc:=sqrt(sqr(xb-xc)+sqr(yb-yc));

p:=(ab+bc+ac)/2;

s:=sqrt(p*(p-ab)*(p-ac)*(p-bc));

writeln(s:4:2);

readln;

end.

Í B nhé

uses crt;

var xa,ya,xb,yb,xc,yc,p,s,ab,bc,ac:real;

begin

clrscr;

readln(xa,ya,xb,yb,xc,yc);

ab:=sqrt(sqr(xa-xb)+sqr(ya-yb));

ac:=sqrt(sqr(xa-xc)+sqr(ya-yc));

bc:=sqrt(sqr(xb-xc)+sqr(yb-yc));

p:=(ab+bc+ac)/2;

s:=sqrt(p*(p-ab)*(p-ac)*(p-bc));

writeln(s:4:2);

readln;

end.

Câu 1: 

uses crt;

var xa,ya,xb,yb,xc,yc,p,s,ab,bc,ac:real;

begin

clrscr;

readln(xa,ya,xb,yb,xc,yc);

ab:=sqrt(sqr(xa-xb)+sqr(ya-yb));

ac:=sqrt(sqr(xa-xc)+sqr(ya-yc));

bc:=sqrt(sqr(xb-xc)+sqr(yb-yc));

p:=(ab+bc+ac)/2;

s:=sqrt(p*(p-ab)*(p-ac)*(p-bc));

writeln('Chu vi la: ',p*2:4:2);

writeln('Dien tich la: ',s:4:2);

readln;

end.

e cảm ơn ạ