How to simplify an exponentional equation?

Question

Is it the best way for the expression of this equation:

$$x = \frac{yexp\big(z(t_1 - t_2)\big)}{1+exp\big({z(t_1 - t_2)}\big)}$$

Answer 1

$$x = y\sigma(z(t_1-t_2))$$

where $\sigma$ is the sigmoid function.

$$ \sigma(t) = \frac{1}{1+e^{-t}} $$