4.
program ctpt;
uses crt;
var t: intger;
begin
clrscr;
write('Nhap so tuoi cua mot nguoi: '); readln(t);
if t<18 then write('Thieu nien') else
if t<40 then write('Thanh nien') else
if t<60 then write('Trung nien') else
write('Lao nien');
readln
end.
5.
program ctpt;
uses crt;
var b, c: integer;
begin
clrscr;
write('Nhap b = '); readln(b);
write('Nhap c = '); readln(c);
if (b=0) and (c=0) then write('Phuong trinh vo so nghiem');
if (b=0) and (c<>0) then write('Phuong trinh vo nghiem');
if (b<>0) then write('Phuong trinh co nghiem x = ', -c/b);
readln
end.
6.
program ctpt;
uses crt;
var t: real;
begin
clrscr;
write('Nhap so KW ma gia dinh da dung trong thang: '); readln(t);
if t<200 then write('Muc tien la 15 000d/KW');
if (t>=200) or (t<=500) then write('Muc tien la 2000d/KW');
if t>500 then write('Muc tien la 2500d/KW');
readln
end.
