The form of the exponential function is
a is the initial amount
b is the growth/decay factor
If
Then the function is growth (increasing)
Compare function (1) by the form above, then
a = 1
b = 2
Since b > 1, then
f(x) is an increasing function
compare function (2) by the form above, then
a = 1
b = 1/2
Since 0 < b < 1, then
g(x) is a decreasing function