2002²-2001×2003-999²
=2002²-(2002-1)×(2002+1)-999²
=2002²-2002² +1-999²
=(1+999)(1-999)
=1000x-998
=-998000
a²-4a+b²+4b+8=0
(a-2)²+(b+2)²=0
a=2 b=-2
3a+(b/2)^2005
=3x2+(-1)^2005
=5