4.

   a)

FOR...DO:

uses crt;

var i: integer;

begin

clrscr;

for i:=30 to 90 do if i mod 2 = 0 then write(i,' ');

readln;

end.

WHILE...DO:

uses crt;

var i: integer;

begin

clrscr;

i:=30;

while i<=90 do

begin

if i mod 2 <> 0 then write(i,' ');

i:=i+1;

end;

readln;

end.

   b)

FOR...DO:

uses crt;

var i: integer;

begin

clrscr;

for i:=120 downto 50 do if i mod 2 = 0 then write(i,' ');

readln;

end.

WHILE...DO:

uses crt;

var i: integer;

begin

clrscr;

i:=120;

while i<=50 do

begin

if i mod 2 <> 0 then write(i,' ');

i:=i-1;

end;

readln;

end.

   c)

S1=40+42+44+….+90

FOR...DO:

uses crt;

var s1,i: integer;

begin

clrscr;

for i:=40 to 90 do if i mod 2 = 0 then s1:=s1+i;

write('S1=',s1);

readln;

end.

WHILE...DO:

uses crt;

var s1,i: integer;

begin

clrscr;

i:=40;

while i<=90 do

begin

if i mod 2 = 0 then s1:=s1+i;

i:=i+1;

end;

write('S1=',s1);

readln;

end.

S2= 67+69+….+231+234

FOR...DO:

uses crt;

var s2,i: integer;

begin

clrscr;

for i:=67 to 231 do if i mod 2 <> 0 then s2:=s2+i;

s2:=s2+234;

write('S2=',s2);

readln;

end.

WHILE...DO:

uses crt;

var s2,i: integer;

begin

clrscr;

i:=67;

while i<=231 do

begin

if i mod 2 <> 0 then s2:=s2+i;

i:=i+1;

end;

s2:=s2+234;

write('S2=',s2);

readln;

end.

S3=1+1/8+1/27+……..1/1000

FOR...DO:Uses crt;
Var i: longint;
    s3: real;
begin
clrscr;
s:=1;
for i:=2 to 10 do
s3:=s3+1/(i*i*i);
write(‘S3=‘,s:10:2);
readln;
end.

S4=5+6+7+…+n

FOR...DO:

uses crt;

var i,s4: integer;

begin

clrscr;

write('Nhap n:');      readln(n);

if n>50 then begin for i:=5 to n do s4:=s4+i; write('S4=',s4); end else write('N<=50 vui long nhap lai');

readln;

end.