1997x19961996-1996x19971997
=1997X(1996X10000+1996)-1996X(1997X10000+1997)
=1997X1996X10000+1997X1996-1996X1997X10000-1996X1997
=0
=(1996+1)*19961996-1996*(19961996+10001)
=19961996-1996*10001
=1996*10001-1996*10001
=0
1997x19961996-1996x19971997
=1997*1996*10001-1996*1997*10001
=0
1997x19961996-1996x19971997
=1997*1996*10001-1996*1997*10001
=0
=1997*1996*10001-1996*1997*10001
=0