a的平方-5a-2003=0
a^2-5a=2003
[(a-2)的三次方-(a-1)的平方+1]/(a-2)的值
=(a-2)^2-[(a^2-2a+1)-1]/(a-2)
=(a^2-4a+4)-a(a-2)/(a-2)
=(a^2-4a+4)-a
=a^2-5a+4
=2003+4
=2007