1996^3+1997*1995-1997*1996^2
=1996^3+(1996+1)*(1996-1)-(1996+1)*1996^2
=1996^3+(1996^2-1)-(1996^3+1996^2)
=1996^3+1996^2-1-1996^3-1996^2=-1
1996^3+1997*1995-1997*1996^2
=1996^3+(1996+1)*(1996-1)-(1996+1)*1996^2
=1996^3+(1996^2-1)-(1996^3+1996^2)
=1996^3+1996^2-1-1996^3-1996^2=-1