Answer:
g(x) = Negative two-fifths(10)x
Step-by-step explanation:
In order to reflect a function over the x-axis, you have to multiply the function by minus one.
Given the function:
f(x) = 2/5(10)^x
Its reflection over the x-axis is:
-f(x) = -2/5(10)^x = g(x)