Would these observations be the same if $\Delta \mathrm{ADM}$ is reflected in the $x$-axis (instead of the $y$-axis)? [Page No. 11]

Yes. A reflection across the x-axis also preserves all side lengths and angles, so the reflected triangle is congruent to the original. In this reflection, the x-coordinates remain the same and the y-coordinates change sign:

A(3, 4) → A'(3, -4)

D(7, 1) → D'(7, -1)

M(9, 6) → M'(9, -6)

Thus, the shape and size remain unchanged, but the triangle is flipped across the x-axis.