13.
uses crt;
var i,n:longint; s:real;
begin
clrscr;
write('Nhap n: ');readln(n);
for i:=2 to n do
s:=s+(i-1)/i;
writeln('S= ',s:0:5);
readln
end.
14.
uses crt;
var i,n,lt,gt:longint; s:real;
begin
clrscr;
write('Nhap n: ');readln(n);
lt:=-1; gt:=1;
for i:=1 to n do
begin
lt:=lt*-1;
gt:=gt*i;
s:=s+lt*(1/gt);
end;
writeln('S= ',s:0:5);
readln
end.
15.
uses crt;
var i,n:longint; s:real;
begin
clrscr;
write('Nhap n: ');readln(n);
for i:=1 to n do s:=sqrt(2+s);
writeln('S= ',s:0:5);
readln
end.
