suppose f(r1)=0, f((r1-2)+2)=f(2-(r1-2)=f(4-r1)=0,
so, both r1 and 4-r1 are roots of the f(x).
If there are four distinct real roots, there must be r1, 4-r1, r2, 4-r2, that makes sum of root=8
猜一下,有可能不对,
所有跟帖:
• 回复:猜一下,有可能不对, -xyz- ♀ (431 bytes) () 01/01/2013 postreply 14:43:48