1.原式=x^2+2x+1-4x^2+9
=-3x^2+2x+10
2.原式=(x-z)^2-4y^2
=x^2-2xz+z^2-4y^2
=x^2-4y^2+z^2-2xz
3.原式=(2007-1)(2007+1)
=2007^2-1
=4028048