If the image of the point (2, 1) with respect to a line mirror is (5, 2), find the equation of the mirror.
Given: image of (2 1) is (5,2)
To find:
The equation of the mirror.
Explanation:
Let the image of A (2, 1) be B (5, 2).
Also, let M be the midpoint of AB.
∴ Coordinates of M
Diagram:
Let CD be the mirror.
Line AB is perpendicular to the mirror CD.
∴ Slope of AB × Slope of CD = − 1
⇒ Slope of CD = -1
⇒ Slope of CD = -3
Equation of the mirror CD
⇒ 2y – 3 = -6 x + 21
⇒ 6x + 2y – 24 = 0
⇒ 3x + y -12 = 0
Hence, the equation of mirror is 3x + y -12 = 0