Nếu có lỗi thì bạn nói mình nhé. ^^
program Hello;
uses crt;
var a:array[1..100] of longint;
x,y,i,j,n,p1,p2:longint;
begin
clrscr;
p1:=0;
write('n = ');
readln(n);
for i:=1 to n do
read(a[i]);
for i:=1 to n do
for j:=i to n do
begin
p2:=abs(a[i]-a[j])*abs(a[i]+a[j]);
if abs(x)=abs(a[i]) then
x:=abs(x);
if abs(y)=abs(a[j]) then
y:=abs(y);
if p1<=p2 then
begin
p1:=p2;
x:=a[i];
y:=a[j];
end;
end;
if x<y then
begin
i:=x;
x:=y;
y:=i;
end;
writeln('|x-y|*|x+y| = ', p1);
write('x = ', x, ' | y = ', y);
end.