So a 10= 1.
Then a1= a10/(q 9) =1/q 9; a2= 1/q^8; a3= 1/q^7; ……
a 10= 1,a 1 1 = a 10 * q = q; a 12=q^2; a 13=q^3; ……; a 19=q^9; ……
So the left inequality A1+A2+A3+...+An =1/Q 9+1/Q 8+1/Q 7+...+1+Q 2+.
On the right of the inequality is1/a1+1/a2+1a3+...+1/an = q 9+q 8+q 7+...+1+.
Compared with ① ②, when n= 19, ① = ②.
When q> 1, make ① >; ②, it must be n> 19.
When 0; ②, which must be 0.