Seeking a tip on show to show convexity in a set.
Allow $f\colon \mathbb{R}^n \rightarrow \mathbb{R}$ be a convex function and also allow $c$ be some constant.
Show that the set $s=\\{x \in \mathbb{R}^n \mid f(x) \le c \\}$ is convex.
Hint : Well, simply list a convex mix of components in s and also validate that it come from s. You will certainly locate the convexity of f valuable for this.
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