What are the coordinates of the reflection of the point (1, 4) in the x-axis?

Difficulty: Easy

Correct Answer: (1, -4)

Explanation:


Introduction / Context:
This coordinate geometry question checks your understanding of reflections in the Cartesian plane. When a point is reflected in the x axis, its horizontal position remains unchanged, while its vertical coordinate changes sign. Knowing this rule allows you to find the new coordinates quickly without complex calculations.


Given Data / Assumptions:

  • Original point: (1, 4).
  • The reflection is taken in the x axis.
  • Coordinates are in the standard (x, y) format.


Concept / Approach:
The rule for reflection in the x axis is simple: a point (x, y) becomes (x, -y). The x coordinate stays the same because reflection occurs vertically across the horizontal axis. The y coordinate changes sign because the point is mirrored to the opposite side of the axis. Applying this rule directly gives the image of the original point.


Step-by-Step Solution:

Step 1: Identify the original coordinates: x = 1 and y = 4. Step 2: Apply the reflection rule in the x axis: (x, y) → (x, -y). Step 3: Keep x the same: x = 1. Step 4: Change the sign of y: y = 4 becomes -4. Step 5: Therefore, the reflected point is (1, -4).


Verification / Alternative check:
You can visualize the Cartesian plane: the x axis is horizontal. The point (1, 4) is one unit to the right of the origin and four units above the x axis. Reflecting it in the x axis puts it one unit to the right of the origin but four units below the x axis, which corresponds to (1, -4). This simple mental picture confirms the calculation.


Why Other Options Are Wrong:

(1, 4): is the original point, not its reflection. (-1, 4): reflects in the y axis, not in the x axis. (-1, -4): reflects in both axes (origin reflection). (4, 1): swaps coordinates and does not correspond to any standard axis reflection for this point.


Common Pitfalls:
Students sometimes mistakenly change the sign of the x coordinate instead of the y coordinate for reflection in the x axis, which actually describes a reflection in the y axis. Another common mistake is swapping coordinates, which corresponds to reflection in the line y = x. Remember that the x axis affects only the vertical coordinate y when reflecting.


Final Answer:
(1, -4)

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