(1)100-98+96-94+92-90+…+8-6+4-2,
=(100-98)+(96-94)+(92-90)+…+(8-6)+(4-2),
=2×25,
=50;
(2)1001×1001-1001
=(1001-1)×1001,
=1000×1001,
=1001000.
(1)100-98+96-94+92-90+…+8-6+4-2,
=(100-98)+(96-94)+(92-90)+…+(8-6)+(4-2),
=2×25,
=50;
(2)1001×1001-1001
=(1001-1)×1001,
=1000×1001,
=1001000.