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Need Solution for R.D.Sharma Maths Class 12 Chapter 27 Straight Line in Space  Exercise 27.4 Question 10  Maths Textbook Solution.

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Answer – The answer of the question is Q\left ( \frac{-3}{2},\frac{-1}{2},4 \right )

(Hint – By putting the value of \gamma ).

Given – Point (0,2,7) and equation of the line \frac{x+2}{-1}=\frac{y-1}{3}=\frac{z-3}{-2}.

Solution - Let PQ be the perpendicular drawn from P to given line whose endpoint/foot is Q point.

Thus to find Distance PQ we have to first find co-ordinates of Q.

\begin{aligned} &* \frac{x+2}{-1}=\frac{y-1}{3}=\frac{z-3}{-2}=\gamma(\text { let }) \\ &* \quad \mathrm{x}=-\gamma-2, y=3 \gamma+1, z=-2 \gamma+3 \\ &:: \text { Co-ordinates of } \mathrm{Q}(-\gamma-2,3 \gamma+1,-2 \gamma+3) \end{aligned}

Hence,

Direction of PQ is

\begin{aligned} &=(-\gamma-2-0),(3 \gamma+1-2),(-2 \gamma+3-7) \\\\ &=(-\gamma-2),(3 \gamma-1),(-2 \gamma-4) \end{aligned}

And by comparing with given line equation, direction ratios of the given line are

( Hint – denominator terms of line equation).

= (-1,3,-2)

:: PQ  is perpendicular at the given line. Therefore, By “ Conditions of Perpendicularity”.

                                                                    a_{1}a_{2}+b_{1}b_{2}+c_{1}c_{2}=0

; whereas a terms and b terms are direction ratio of lines which are perpendicular to each other.

\begin{aligned} &=-1(-\gamma-2)+(3)(3 \gamma-1)-2(-2 \gamma-4)=0 \\ &=\gamma+2+9 \gamma-3+4 \gamma+8=0 \\ &=\gamma=\frac{-1}{2} . \end{aligned}

:: Co-ordinates of Q ,

By putting the value of \gamma  in Q

\begin{aligned} &=Q\left\{-\left(\frac{-1}{2}\right)-3\left(\frac{-1}{2}\right)+1,-2\left(\frac{-1}{2}\right)+3\right\} \\ &=Q\left\{\frac{-3}{2}, \frac{-1}{2}, 4\right\} \end{aligned}

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