1) if x+1/x=2,then x^2012+1/x^2012=?
2)if A>B>C>D,find the digits A,B,C,D (which are from1 to 9), so that
ABCD-DCBA=BDAC.
3)solve:px-qy=r and rx-py=q.
x + 1/x = 2
x = 1
x^n + 1/x^n = 2 for any n
7641-1467=6174
x = p(pr-q^2)/(p^2-rq)
y = (r^2-pq)/(p^2-rq)