应为f(X)是偶函数,所以f(-X) = f(X)
f(5.5)=f(2+2+2+2-2.5)
=-1/f(2+2+2-2.5)
=f(2+2-2.5)
=-1/f(2-2.5)
=f(-2.5)
=f(2.5)
=2.5+1
=3.5