Please use the "caret" sign (^) to indicate exponentiation, and follow rules of PEMDAS for priority of operations, including parentheses.
In general, reflection about the x-axis is achieved by negation of the function.
For example, the reflection of p(x) across the x-axis is q(x)=-p(x).
Assuming f(x)=(2/5)10^x, the reflection of f(x) across the x-axis is
g(x)=-f(x)=-(2/5)10^x.