Bài 1:

Program bai1;
Uses crt;
Var x, y,: integer;
Begin
Clrscr;
Write('x='); readln(x);
Write('y='); readln(y);
Writeln('x^2-y^2',x*x-y*y);
Readln

End.

bài 2

Program bai2;
Uses crt;
Var hs: integer;
Begin
Clrscr;
Write('Nhap so luong hoc sinh cua lop='); readln(hs);
Writeln('So cay lop phai trong la: ',hs*2 );
Readln
End.

program tinh;
uses crt;
var x, y, bt: integer;
begin
clrscr;
write(' nhap so nguyen x:'); readln(x);
write(' nhap so nguyen y:'); readln(y);
bt:= sqr( x) - sqr( y);
writeln(' gia tri cua bieu thuc la:', bt);
readln
end.

bài 2

program trong_cay;
uses crt;
var x, y: integer;
begin
clrscr;
write(' nhap so hoc sinh:'); readln( x);
y:= x* 2;
writeln(' so cay hoc sinh phai trong la: ', y );
readln
end.