2002^2-4*2002+2^2
=2002^2-2*2*2002+2^2
=(2002-2)^2
=2000^2
=4000000
1997^2+6*1997+3^2
=1997^2+2*3*1997+3^2
=(1997+3)^2
=2000^2
=4000000