Bài 4:

program bai_giai;
uses crt;
var a,b,cv,dt:integer;
begin
    clrscr;
    write('Nhap a: '); readln(a);
    write('Nhap b: '); readln(b);
    cv:=(a+b)*2;
    dt:=a*b;
    writeln('Chu vi la: ',cv);
    write('Dien tich la: ',dt);
    readln;
end.

Bài 7:

program bai_giai;
uses crt;
var n,m:integer;
begin
    clrscr;
    write('Nhap n: ');  readln(n);
    m:=abs(n);
    write('|',n,'| = ',m);
    readln;
end.

Bài 8:

program bai_giai;
uses crt;
var n:integer;
    m:real;
begin
    clrscr;
    write('Nhap n: ');  readln(n);
    m:=sqrt(n);
    write('Can bac hai cua ',n,' la: ',m:0:2);
    readln;
end.

Bài 10:

program bai_giai;
uses crt;
var n,m:integer;
begin
    clrscr;
    write('Nhap n: ');  readln(n);
    m:=n mod 10; n:=n div 10;
    m:=m*10+n mod 10; n:=n div 10;
    m:=m*10+n mod 10;
    write('So dao nguoc la: ',m);
    readln;
end.

Bài 4
uses crt;
var a,b,c,s:real;
begin
clrscr;
readln(a,b);
c := 2*(a+b);
s := a*b;
writeln('Chu vi cua hinh chu nhat la ',c:0:2);
writeln('Dien tich cua hinh chu nhat la ',s:0:2);
readln
end.

Bài 7
uses crt;
var n:longint;
begin
clrscr;
readln(n);
writeln('Gia tri tuyet doi = ',abs(n)); 
readln
end.

Bài 8
uses crt;
var n:real;
begin
clrscr;
readln(n);
writeln('Can bac hai = ',sqrt(n):0:2);
readln
end.

Bài 10
uses crt;
var x,y:longint;
begin
clrscr;
readln(x);
 y := 0;
 while(x>0) do
begin
     y := y * 10 + x mod 10;
     x := x div 10;
end;
writeln('So dao nguoc = ',y);
readln
end.