(1+2分之1)*(1-2f分之1)*(1+3分之1)*(1-3分之1)……(1+99分之1)*(1-99分之1)
=(1-1/2)(1+1/2)(1-1/3)(1+1/3)……(1-1/99)(1+1/99)
=(1/2)(3/2)(2/3)(4/3)(3/4)(5/4)……(98/99)(100/99)
=(1/2)(100/99)
=50/99
(1+2分之1)*(1-2f分之1)*(1+3分之1)*(1-3分之1)……(1+99分之1)*(1-99分之1)
=(1-1/2)(1+1/2)(1-1/3)(1+1/3)……(1-1/99)(1+1/99)
=(1/2)(3/2)(2/3)(4/3)(3/4)(5/4)……(98/99)(100/99)
=(1/2)(100/99)
=50/99