问题
解答题
若(N+2005)2=123456789,求(N+2015)(N+1995)的值.
答案
∵(N+2015)(N+1995),
=[(N+2005)+10][(N+2005)-10],
=(N+2005)2-102,
(N+2005)2=123456789,
∴原式=123456789-100=123456689.
若(N+2005)2=123456789,求(N+2015)(N+1995)的值.
∵(N+2015)(N+1995),
=[(N+2005)+10][(N+2005)-10],
=(N+2005)2-102,
(N+2005)2=123456789,
∴原式=123456789-100=123456689.