 Locally compact subspaces are open in Hausdorff compactifications

If a locally compact Hausdorff space is densely embedded in a Hausdorff space, its image is open. Around a point choose an ambient open set whose trace lies in a compact neighborhood $K$. Density puts that ambient open set inside the ambient closure of its trace, which lies in $K$ because compact subsets of a Hausdorff space are closed. Thus the ambient open set lies in the image.