Mathematics
If the point P(a, b) is first reflected in the origin and then reflected in the y-axis to the point P"(-9, -7), then the value of (2a - 3b) is :
-16
-25
-3
-39
Reflection
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Answer
Given, point P(a, b).
On reflection in origin, the sign of x-coordinate and y-coordinate changes.
(a, b) ⇒ (-a, -b)
On reflection in y-axis, the sign of x-coordinate changes.
(-a, -b) ⇒ (a, -b)
Given, final point P'(-9, -7)
∴ (a, -b) = (-9, -7)
⇒ a = -9 and -b = -7
⇒ a = -9 and b = 7
⇒ 2a - 3b = 2(-9) - 3(7)
⇒ -18 - 21
⇒ -39.
Hence, Option 4 is the correct option.
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