Rearranging Equations

Question

How can I get from the first image to the second image? I've tried various ways but how does the exponential end up with a negative in front of it?

Answer 1

HINT: multiply numerator and denominator by $$e^{-2\sqrt{Cg}t}$$

Answer 2

Hint: Multiply the RHS by $$ \frac{e^{-2\sqrt{Cg}t}}{e^{-2\sqrt{Cg}t}} $$