Question

3乘5分之1加5乘7分之一...加2005乘2007分之一

Answer 1

1/(3*5)=0.5*(1/3-1/5)

1/(5*7)=0.5*(1/5-1/7)

...

...

...

1/(2005*2007)=0.5*(1/2005-1/2007)

相加就是0.5*(1/3-1/2007)=334/2007