a) =2002 + 2(1+2+3+.......+2001) = 2002 + 2x(2001+1)(2001)/2 =
2002 +2002x2001 =2002 (1+2001) =2002^2
b)3+6+9+.....+6006 -2003x1000 =3(1+2+3+...+2002) -2003x1000=
3(2002+1)(2002/)2 -2003x1000= 3x2003x1001-2003x1000=
2003(3x1001-1000) =2003(3003-1000) =2003x2003 = 2003^2