2/

uses crt;

var i,n,a: integer;

s: real;

begin

clrscr;

write ('nhap n: ');   readln (n);

write ('nhap a: ');   readln (a);

s:=0;

for i:=1 to n do

s:=s+(1/(a+i));

writeln ('tong la: ',s:1:2);

readln;

end.

3/

uses crt;

var i,n,s: integer;

begin

clrscr;

write ('nhap n: ');   readln (n);

s:=0;

for i:=1 to n do

if i mod 2=1 then s:=s+i;

writeln ('tong la: ',s);

readln;;

end.

4/

uses crt;

var a,i,n:integer;

s: longint;

begin

clrscr;

write ('nhap n: ');   readln (n);

write ('nhap a: ');   readln (a);

s:=0;

for i:=1 to n do

if i mod 2=0 then

s:=s+(a+i);

writeln ('tong la: ',s);

readln;

end.

Câu 2:

Program bai2;

Uses crt;

Var a,n:integer;

      S,x:real;

Begin

Clrscr;

Write('a='); Readln(a);

S:=0;

n:=1;

x:=1/(a+1);

While x>=0.0001 do

     Begin

     S:=S+n/(a+n);

     x:=n/(a+n);

     n:=n+1;

     End;

Writeln('S=',S:9:3);

Readln

End.

Câu 3:

Program bai3;

Uses crt;

Var S,n:integer;

Begin

Clrscr;

n:=1;

S:=0;

While S<=1500 do

     Begin

     S:=S+n;

     n:=n+2;

     End;

Writeln('n=',n);

Writeln('S=',S);

Readln

End.

Câu 4:

Program bai4;

Uses crt;

Var n,a:integer;

      S:longint;

Begin

Clrscr;

randomize;

a:=random(100);

n:=2;

S:=0;

While S<=1500 do

     Begin

     S:=S+(a+n);

     n:=n+2;

     End;

Writeln('n=',n);

Writeln('S=',S);

Readln

End.