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The coordinates of the foot of the perpendicular from the point (1, $$-$$2, 1) on the plane containing the lines, $${{x + 1} \over 6} = {{y - 1} \over 7} = {{z - 3} \over 8}$$ and $${{x - 1} \over 3} = {{y - 2} \over 5} = {{z - 3} \over 7},$$ is :

JEE · Math · previous-year question

  1. A.(2, $$-$$4, 2)
  2. B.($$-$$ 1, 2, $$-$$1)
  3. C.(0, 0, 0)correct
  4. D.(1, 1, 1)

Answer

C. (0, 0, 0)

Explanation

$$\overrightarrow n $$ = $$\overrightarrow {{n_1}} \times \overrightarrow {{n_2}} $$ = $$\left| {\begin{matrix} {\widehat i} & {\widehat j} & {\widehat k} \\ 6 & 7 & 8 \\ 3 & 5 & 7 \\ \end{matrix} } \right|$$ = (9, $$-$$ 18, 9) = (1, $$-$$2, 1) $$ \therefore $$ Equation of plane is 1(x + 1) $$-$$ 2(y $$-$$ 1) + (z $$-$$ 3) = 0 $$ \Rightarrow $$ x $$-$$ 2y + z = 0 foot to z $${{x - 1} \over 1}$$ = $${{y + 2} \over { - 2}}$$ = $${{z - 1} \over 1}$$ = $$ - {{\left[ {1 + 4 + 1} \right]} \over 6}$$ x = 0, y = 0, z = 0

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