1/1x3=1/2(1-1/3),1/3x5=1/2(1/3-1/5),1/5x7=1/2(1/5-1/7),……,1/17x19=1/2(1/17-1/19).∴1/1x3+1/3x5+1/5x7+……+1/17x19
=1/2(1-1/3)+1/2(1/3-1/5)+1/2(1/5-1/7)+……+1/2(1/17-1/19)
=1/2 (1-1/3+1/3-1/5+1/5-1/7+……+1/17-1/19)
=1/2(1-1/19)
=9/19
根據(jù)以上材料,回答下列問題：
（1）在式子1/1x3+1/3x5+1/5x7+……中第五項(xiàng)是________
(2)寫出第n個(gè) 等式,并證明
(3)當(dāng)m=4時(shí)計(jì)算1/m(m+4)=1/(m+4)(m+8)+.+1/(m+92)(m+96)的值