已知(a+100)=2009,求(a+101)(a+99)
问题描述：
已知(a+100)=2009,求(a+101)(a+99)
答
(a+101)(a+99) =(a+100+1)(a+100-1) =(a+100)^2-1^2 =2009^2-1 =2009*2009-1 =4036080
已知(a+100)=2009,求(a+101)(a+99)
(a+101)(a+99) =(a+100+1)(a+100-1) =(a+100)^2-1^2 =2009^2-1 =2009*2009-1 =4036080