1-1/2+1/3-1/4+1/5-1/6+.+1/99-1/100
=(1+1/2+1/3+.+1/99+1/100)-2*(1/2+1/4+1/6+.+1/100)
=(1+1/2+1/3+.+1/99+1/100)-(1+1/2+1/3+.+1/50)
=1/51+1/52+1/53+.+1/100
=2*(1/102+1/104+1/106+...+1/200)*
因此两边是相等的,