Question

例1：已知数列根号5,根号11,根号17,根号23,根号29……,则5根号5是它的第几项式?

Answer 1

a1*a1=5

a2*a2=11

a3*a3=17

.

数列[an*an]为等差数列

an*an=5+(n-1)*6=6n-1

（5根号5）*（5根号5）=6n-1

n=21