a2？ =a 1a3

a 1a2a3=2 16

So a2? =2 16

a2=6

a 1=6/q，a3=6q

Then 6/q+6+6q=26.

Multiply both sides by q

3q？ - 10q+3=0

(3q- 1)(q-3)=0

q= 1/3，q=3

So it's 2,6, 18 or18,6,2.