C=c.3/4+c.5/6-c.19/12
=c.(3/4+5/6-19/12)
=c.0
=0
Vậy C=0
Thay c = 2002/2003 vào, ta có:
C = 2002/2003 . 3/4 + 2002/2003 . 5/6 - 2002/2003 . 19/12
C = 2002/2003 . (3/4 + 5/6 - 19/12)
C = 2002/2003 . (9/12 + 10/12 - 19/12)
C = 2002/2003 . 0
C = 0