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JEE Mains · Maths · STD 12 - 11. three dimension geometry

Let the mirror image of the point \((a, b\), c) with respect to the plane \(3 x-4 y+12 z+19=0\) be (a- \(6, \beta, \gamma)\). If \(a+b+c=5\), then \(7 \beta-9 \gamma\) is equal to

  1. A \(127\)
  2. B \(147\)
  3. C \(157\)
  4. D \(137\)
Verified Solution

Answer & Solution

Correct Answer

(D) \(137\)

Step-by-step Solution

Detailed explanation

\(M =\left(a-3, \frac{\beta+b}{2}, \frac{\gamma+c}{2}\right)\) Since \(M\) lies on \(3 x+4 y+12 z+19=0\) \(\Rightarrow 6 a-4 b+12 c-4 \beta+12 \gamma+20=0 \text {. }\) Since \(PP'\) is parallel to normal of the plane then \(\frac{6}{3}=\frac{b-\beta}{-4}=\frac{c-\gamma}{12}\)…