1. Let's analyze the expression $4x - 2x$. 2. Combine like terms: $4x - 2x = (4 - 2)x = 2x$. 3. The expression simplifies to $2x$. 4. Whether $2x$ is positive depends on the value of $x$. 5. If $x > 0$, then $2x > 0$, so the expression is positive. 6. If $x = 0$, then $2x = 0$, so the expression is zero. 7. If $x < 0$, then $2x < 0$, so the expression is negative. 8. Therefore, $4x - 2x$ is positive only when $x$ is positive.