an=1+1/[n*(n+2)]=[n(n+2)+1]/[n(n+2)]=(n+1)^2/[n(n+2)] n=1,2,3.
a1=2^2/(1*3)
a2=3^2/(2*4)
a3=4^2/(3*5)
a4=5^2/(4*6)
.
a98=99^2/(98*100)
注:a1*a2*a3*a4=2*5/6 a2的3的平方可以与a1和a3的分母的3可以约掉,依次内推
a1a2a3...a98=2*99/100=1.98
an=1+1/[n*(n+2)]=[n(n+2)+1]/[n(n+2)]=(n+1)^2/[n(n+2)] n=1,2,3.
a1=2^2/(1*3)
a2=3^2/(2*4)
a3=4^2/(3*5)
a4=5^2/(4*6)
.
a98=99^2/(98*100)
注:a1*a2*a3*a4=2*5/6 a2的3的平方可以与a1和a3的分母的3可以约掉,依次内推
a1a2a3...a98=2*99/100=1.98