Bài 1 Var i,n:integer; s:longint; Function nt(a:integer):boolean; Var b,dem:integer; Begin dem:=0; For b:=1 to a do if a mod b = 0 then dem:=dem+1; if dem = 2 then nt:=true else nt:=false; End; BEGIN Write('Nhap N: '); Readln(n); If ((n mod 2) <> 0) then for i:= 2 to n do if nt(i) then s:=s+i; if n mod 2 = 0 then for i:=1 to n do if (i mod 2) <> 0 then s:=s+i*i; Writeln('Tong S=',s); readln; END. Bài 2 Var i,j,k,n,x,y,z,dem: integer; BEGIN Write('Nhap so tien can rut ( n<= 10000): '); readln(n); Write('Nhap 3 loai tien ma may co (x,y,z<=500) : '); readln(x,y,z); For i:=0 to n div x do for j:=0 to n div y do for k:=0 to n div z do if i*x +j*y +k*z = n then begin Dem:=dem+1; Writeln('Cach ',dem,': So tien loai ',x,'; ',y,'; ',z,'; lan luot la: ',i*x,'; ',j*y,'; ',k*z,'.'); end; if dem= 0 then Write('Khong co cach nao de rut dung so tien yeu cau') else Writeln('Co tat ca ',dem,' cach rut tien'); readln; END. Bài 3 uses crt; Var i,t,k1,k2: integer; j,g: char; s1,s2: String; BEGIN Write('Nhap xau ky tu : '); Readln(s1); For i:=1 to length(s1) do s1[i]:=Upcase(s1[i]); For i:=1 to length(s1) do For j:='A' to 'Z' do Begin if j=s1[i] then begin t:= (k1+5) mod 26; k2:=0; for g:='A' to 'Z' do begin if k2=t then s2:=s2+g; k2:=k2+1; end; end; k1:=k1+1; end; Write(' Xau ky tu tren duoc ma hoa la: ',s2); Readln; END. . Bài 1 Var i,n:integer; s:longint; Function nt(a:integer):boolean; Var b,dem:integer; Begin dem:=0; For b:=1 to a do if a mod b = 0 then dem:=dem+1; if dem. S=',s); readln; END. Bài 2 Var i,j,k,n,x,y,z,dem: integer; BEGIN Write('Nhap so tien can rut ( n<= 10000): '); readln(n); Write('Nhap 3 loai tien ma may co (x,y,z<=500). Writeln('Cach ',dem,': So tien loai ',x,'; ',y,'; ',z,'; lan luot la: ',i*x,'; ',j*y,'; ',k*z,'.'); end; if dem= 0 then