Does the subtraction of strictly increased and strictly decreased function has only one zero (at most)?

Question

I have the following expression:

$y(x)=f(x)-g(x)$

$f(x)$ is positive and strictly increased at the interval $x->[0 \ x_0]$

$g(x)$ is positive and strictly decreased at the interval $x->[0 \ x_0]$

Can I say or prove that $y(x)$ has at the most one zero?