答：
x^2-5x-2013=0
[ (x-2)^2 -(x-1)^2+1]/(x-2)
=[(x-2+x-1)*(x-2-x+1)+1 ] /(x-2)
=(-2x+3+1)/(x-2)
=(-2x+4) /(x-2)
=-2