Apply to a specific x

From CS2800 wiki

If you know [math]P [/math] holds for all [math]x [/math], then you can conclude [math]P [/math] holds for any specific [math]x [/math]. For example, if you know for all [math]x \href{/cs2800/wiki/index.php/%E2%88%88}{∈} ℝ [/math], [math]x^2 ≥ 0 [/math], then you can conclude [math]7^2 ≥ 0 [/math] (since [math]7 ∈ ℝ [/math]).