Convert to Interval Notation 0<=f(x)

$0 \leq f (x)$

Rewrite so $f$ is on the left side of the inequality.

$f (x) \geq 0$

Subtract $f (x)$ from both sides of the inequality.

$0 \geq - f (x)$

Convert the inequality to interval notation.

$[- f (x), \infty)$