Mirror Images — Revision Notes

⚡ 30-Second Revision

Vertical mirror: preserve y; reflect x about the stated line.
At x = a: image x = 2a - x.
Check a marker and an arrow, not just the border.
Reflection twice in the same line restores the figure.
Original spatial practice; no claimed PYQ frequency.

2-Minute Revision

A vertical mirror keeps each point at the same height and places it equally far on the opposite side of the line. The formula (-x, y) applies only when that line is x = 0. For a shifted line, use equal distances or 2a - x.

Track asymmetric interior features to distinguish reflection from rotation. A horizontal row reverses order, but each shape also needs its own reflection. Symmetry of the outer boundary alone does not establish symmetry of the complete figure.

Check the answer by reflecting it back.

5-Minute Revision

Reflect and compare

Points P(1, 4), Q(3, 1) and R(4, 5) form a marked figure. Reflect it across x = 6. The images are P′(11, 4), Q′(9, 1) and R′(8, 5). Each pair has midpoint x = 6 and unchanged y.

Now compare the proposed alternative P′(11, -4). Its horizontal placement is correct, but its height has changed. It combines an additional vertical reversal with the required operation and therefore fails.

Reflect Q′ back: 12 - 9 = 3, restoring Q(3, 1). Explain why a point lying on x = 6 would remain fixed. This exercise tests the reference line, preserved coordinate and reversibility separately.

Vyyuha Quick Recall

L-H-D: Line first, Height unchanged, equal Distance across the line.