987654321×123456789,
=987654321×(123456788+1),
=987654321×123456788+987654321,
987654322×123456788,
=(987654321+1)×123456788,
=987654321×123456788+123456788,
因987654321×123456788+987654321>987654321×123456788+123456788,
所以987654321×123456789>987654322×123456788.
故答案为:a>b.