a4 |
a2 |
∴q=2,a1=
a2 |
q |
因此
lgan+1+lgan+2+…+lga2n |
n |
lg2n+1+lg2n+2+…+lg22n |
n2 |
=
[(n+1)+(n+2)+…+2n] |
n2 |
=
3n2+n |
2n2 |
原式=
lim |
n→∞ |
3n2+n |
2n2 |
lim |
n→∞ |
3n2+n |
2n2 |
3 |
2 |
lim |
n→∞ |
lgan+1+lgan+2+…+lga2n |
n |
a4 |
a2 |
a2 |
q |
lgan+1+lgan+2+…+lga2n |
n |
lg2n+1+lg2n+2+…+lg22n |
n2 |
[(n+1)+(n+2)+…+2n] |
n2 |
3n2+n |
2n2 |
lim |
n→∞ |
3n2+n |
2n2 |
lim |
n→∞ |
3n2+n |
2n2 |
3 |
2 |