How are the two functions f (x) = 0.7 (6) ^x and g (x) = 0.7^-x related to each other?

To find the relationship between them, lets do some algebra:

f (x) = (7/10) ^x

g (x) = (7/10) ^-x

if we do:

f (x) * g (x) = 1

due to exponents multiplying addition law, therefore, the relationship, gives:

f (x) = 1 / g (x)