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JEE Main 20266 AprilEvening Shift
Exam
JEE Main
Year
2026
Date
6 April
Shift
Evening Shift
Subject
Mathematics
Chapter
Three Dimensional Geometry

JEE Main 2026 · 6 April · Evening Shift · Mathematics · Three Dimensional Geometry

Let the image of the point P(0, -5, 0) in the line (x-1)/(2) =...

Let the image of the point P(0,−5,0)P(0, -5, 0) in the line x−12=y1=z+1−2\dfrac{x-1}{2} = \dfrac{y}{1} = \dfrac{z+1}{-2} be the point RandtheimageofthepointR and the image of the pointQ(0,−12,0)Q\left(0, \dfrac{-1}{2}, 0\right) in the line x−1−1=y+94=z+11\dfrac{x-1}{-1} = \dfrac{y+9}{4} = \dfrac{z+1}{1} be the point SS. Then the square of the area of the parallelogram PQRSPQRS is __________.

Correct answer

0

Step-by-step solution

Let M1M_1 be the foot of the perpendicular from P(0,−5,0)P(0, -5, 0) to the first line L1:x−12=y1=z+1−2L_1: \dfrac{x-1}{2} = \dfrac{y}{1} = \dfrac{z+1}{-2}.
A general point on L1L_1 is M1(2λ+1,λ,−2λ−1)M_1(2\lambda + 1, \lambda, -2\lambda - 1).
The direction ratios of PM1PM_1 are (2λ+1,λ+5,−2λ−1)(2\lambda + 1, \lambda + 5, -2\lambda - 1).
Since PM1PM_1 is perpendicular to L1L_1, their dot product is zero:
2(2λ+1)+1(λ+5)−2(−2λ−1)=02(2\lambda + 1) + 1(\lambda + 5) - 2(-2\lambda - 1) = 0
4λ+2+λ+5+4λ+2=0⇒9λ+9=0⇒λ=−14\lambda + 2 + \lambda + 5 + 4\lambda + 2 = 0 \Rightarrow 9\lambda + 9 = 0 \Rightarrow \lambda = -1
Thus, M1M_1 is (−1,−1,1)(-1, -1, 1).

Let M2M_2 be the foot of the perpendicular from Q(0,−12,0)Q\left(0, \dfrac{-1}{2}, 0\right) to the second line L2:x−1−1=y+94=z+11L_2: \dfrac{x-1}{-1} = \dfrac{y+9}{4} = \dfrac{z+1}{1}.
A general point on L2L_2 is M2(−μ+1,4μ−9,μ−1)M_2(-\mu + 1, 4\mu - 9, \mu - 1).
The direction ratios of QM2QM_2 are \left(-\mu + 1, 4\mu - \dfrac{17}{2}, \mu - 1\right).<br>Since.<br>SinceQM_2isperpendiculartois perpendicular toL_2,theirdotproductiszero:<br>, their dot product is zero:<br>-1(-\mu + 1) + 4\left(4\mu - \dfrac{17}{2}\right) + 1(\mu - 1) = 0<br><br>\mu - 1 + 16\mu - 34 + \mu - 1 = 0 \Rightarrow 18\mu - 36 = 0 \Rightarrow \mu = 2<br>Thus,<br>Thus,M_2isis(-1, -1, 1).<br><br>Since.<br><br>SinceM_1andandM_2arethesamepointare the same pointM(-1, -1, 1),thediagonals, the diagonalsPRandandQSofthequadrilateralof the quadrilateralPQRSbisecteachotheratbisect each other atM.Therefore,. Therefore,PQRSisaparallelogram.<br><br>Theareaoftheparallelogramisgivenbyis a parallelogram.<br><br>The area of the parallelogram is given by\dfrac{1}{2} |\overrightarrow{PR} \times \overrightarrow{QS}|.<br>Wehave:<br>.<br>We have:<br>\overrightarrow{PR} = 2\overrightarrow{PM} = 2(-1 - 0, -1 - (-5), 1 - 0) = (-2, 8, 2)<br><br>\overrightarrow{QS} = 2\overrightarrow{QM} = 2\left(-1 - 0, -1 - \left(\dfrac{-1}{2}\right), 1 - 0\right) = (-2, -1, 2)<br><br>Now,computethecrossproduct<br><br>Now, compute the cross product\overrightarrow{PR} \times \overrightarrow{QS}:<br>:<br>\overrightarrow{PR} \times \overrightarrow{QS} = \begin{vmatrix} \hat{i} & \hat{j} & \hat{k} \\ -2 & 8 & 2 \\ -2 & -1 & 2 \end{vmatrix} = \hat{i}(16 - (-2)) - \hat{j}(-4 - (-4)) + \hat{k}(2 - (-16)) = 18\hat{i} + 18\hat{k}<br><br>Theareaoftheparallelogramis:<br><br><br>The area of the parallelogram is:<br>\text{Area} = \dfrac{1}{2} |18\hat{i} + 18\hat{k}| = \dfrac{1}{2} \sqrt{18^2 + 18^2} = \dfrac{18\sqrt{2}}{2} = 9\sqrt{2}<br><br>Thesquareoftheareais<br><br>The square of the area is(9\sqrt{2})^2 = 162.<br><br>Answer:.<br><br>Answer:162
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