1002²;-1002*4+4這道題怎麼簡便方法計算?

1002²;-1002*4+4這道題怎麼簡便方法計算?

1002²;-1002*4+4
=1002*(1002-4)+4
=1002*998+4
=(1000+2)*(1000-2)+4
=1000²;-4+4
=1000²;
=1000000