Random Variable - Probability and Statistic Suppose that $f(x)$ is a continuous and symmetric pdf, where symmetry is the property that $f(x) = f(-x)$ for all $x$. Show that $P(-a ≤ X ≤ a) = 2F(a) - 1$
Does anyone have any idea what this is even asking? I have honestly no idea what to do.  

$$ 
P(-a\le X \le a) = F_X(a) - F_X(-a) = F_X(a) - (1-F_X(a)) = 2F_X(a) -1
$$
