[zsy312]

例如展开到五阶：
In[23]:= Series[f[x-1]+f[x+1],{x,0,5}]
Out[23]= (f[-1]+f[1])+((f^\[Prime])[-1]+(f^\[Prime])[1]) x+1/2 ((f^\[Prime]\[Prime])[-1]+(f^\[Prime]\[Prime])[1]) x^2+1/6 ((f^(3))[-1]+(f^(3))[1]) x^3+1/24 ((f^(4))[-1]+(f^(4))[1]) x^4+1/120 ((f^(5))[-1]+(f^(5))[1]) x^5+O[x]^6
In[24]:= Normal[%]
Out[24]= f[-1]+f[1]+x ((f^\[Prime])[-1]+(f^\[Prime])[1])+1/2 x^2 ((f^\[Prime]\[Prime])[-1]+(f^\[Prime]\[Prime])[1])+1/6 x^3 ((f^(3))[-1]+(f^(3))[1])+1/24 x^4 ((f^(4))[-1]+(f^(4))[1])+1/120 x^5 ((f^(5))[-1]+(f^(5))[1])