好难啊……（7的平方-1）分之（7的平方+1）+（9的平方-1）分之（9的平方+1）+（11的平方-1）分之（11的平方

=1+2/(7²-1)+1+2/(9²-1)+…+1+2/(99²-1)
=(99-7)÷2+1+[2/(6×8)+2/(8×10)+…+2/(98×100)]
=47+(1/6-1/8+1/8-1/10+…+1/98-1/100)
=47+(1/6-1/100)
=47+47/300
=47又47/300