Mathematics
If the point P(a, b) is first reflected in the origin and then reflected in the x-axis to the point P"(12, -5), then the value of (b - a) is :
-17
17
7
-7
Reflection
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Answer
Given, point P(a, b).
On reflection in origin, sign on both coordinate changes.
(a, b) ⇒ (-a, -b)
On reflection in x-axis, the sign of y-coordinate changes.
(-a, -b) ⇒ (-a, b)
Given, final point P'(12, -5).
∴ (-a, b) = (12, -5)
⇒ -a = 12 and b = -5
⇒ a = -12 and b = -5.
⇒ b - a = -5 - (-12) = -5 + 12 = 7.
Hence, Option 3 is the correct option.
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