1/a(n+1)-1/an=1
1/an是以1为公差的等差数列
1/an=1/a1+(n-1)d
1/an=1+n-1
1/an=n
an=1/n
an*a(n+1)=1/n*1/(n+1)
=1/n-1/(n+1)
a1a2+a2a3+.+a2010a2011
=1-1/2+1/2-1/3+.+1/2010-1/2011
=1-1/2011
=2010/2011
1/a(n+1)-1/an=1
1/an是以1为公差的等差数列
1/an=1/a1+(n-1)d
1/an=1+n-1
1/an=n
an=1/n
an*a(n+1)=1/n*1/(n+1)
=1/n-1/(n+1)
a1a2+a2a3+.+a2010a2011
=1-1/2+1/2-1/3+.+1/2010-1/2011
=1-1/2011
=2010/2011