Final answer:
The transformation that reflects an object is represented by a reflection matrix. For a reflection in the y-axis, the reflection matrix is R = [-1 0; 0 1].
Step-by-step explanation:
The linear transformation that reflects an object is represented by a matrix called reflection matrix. For a reflection in the y-axis, the reflection matrix is:
R = [-1 0; 0 1]
This means that the x-coordinate of a point remains the same, while the y-coordinate is negated. To reflect a point (x, y) in the y-axis, we multiply the coordinates by the reflection matrix:
R * [x; y] = [-x; y]