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Provide solution for RD Sharma maths class 12 chapter 27 Straight Line in Space exercise 27.1 question 14 maths textbook solution

Answers (1)

Answer :-

\left ( x,y,z \right )=\left ( -2,-1,3 \right ) or \left ( 4,3,7 \right )

Hint :-

Distance Formula : \sqrt{\left(x_{1-} x_{2}\right)^{2}+\left(y_{1-} y_{2}\right)^{2}+\left(z_{1-} z_{2}\right)^{2}} 

Given :-

Point are P (1 , 3 , 3)

And line are  \frac{x+2}{3}=\frac{y+1}{2}=\frac{z-3}{2}

Solution :-

\frac{x+2}{3}=\frac{y+1}{2}=\frac{z-3}{2}  -------- (1)

Let the point be x_{1},y_{1},z_{1}

\therefore \frac{x+2}{3}=\frac{y+1}{2}=\frac{z-3}{2}=\lambda \left ( say \right )

x_{1}=3\lambda -2       ,      y_{1}=2\lambda -1      ,     z_{1}=2\lambda +3

The distance of \left ( x_{1},y_{1},z_{1} \right )  and P (1 , 3 , 3) = 5

                        \sqrt{(3 \lambda-2-1)^{2}+(2 \lambda-1-3)^{2}+(2 \lambda+3-3)^{2}}=5

Squaring both sides

     \begin{aligned} &(3 \lambda-3)^{2}+(2 \lambda-4)^{2}+(2 \lambda)^{2}=25 \\ &\Rightarrow 9 \lambda^{2}-18 \lambda+9+4 \lambda^{2}-16 \lambda+16+4 \lambda^{2}=25 \\ &\Rightarrow 17 \lambda^{2}-34 \lambda=0 \\ &\Rightarrow 17 \lambda(\lambda-2)=0 \\ &\lambda=0, \lambda=2 \end{aligned}

∴ when \lambda =0;x=-2        ,      y=-1     ,      z=3

& when \lambda =2;x=4        ,      y=3     ,      z=7

\left ( x,y,z \right )=\left ( -2,-1,3 \right ) or \left ( 4,3,7 \right )

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