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Explain solution RD Sharma class 12 chapter 28 The Plane exercise multiple choice question 12 maths

Answers (1)

Answer:

 Option (c)

Hint:

 The plane, must satisfy both the equation.

Given:

 \frac{x-3}{1}=\frac{y-4}{2}=\frac{z-5}{2}

Solution:

Let, the point of intersection of the line

\frac{x-3}{1}=\frac{y-4}{2}=\frac{z-5}{2}

And the plane x + y + z = 17 be (x0, y0, z0) So, (x0, y0, z0) satisfy the both equations,

\begin{aligned} &\frac{x_0-3}{1}=\frac{y_0-4}{2}=\frac{z_0-5}{2}=k, \text { (Let) }\\ &\text { i.e. }x_0=k+3\\ &y_0=2k+4\\ &z_0=2k+5 \end{aligned}

Put these values in the equation of plane x + y + z = 17

\begin{aligned} &(k+3)+(2k+4)+(2k+5)=17\\ &5k+12=17\\ &k=1\\ &\therefore x_0=1+3\\ &=4\\ &y_0=2\times 1+4\\ &=6\\ &z_0=2\times 1+5\\ &=7\\ \end{aligned}

Hence, the distance between point (4, 6, 7) and (3, 4, 5) is,

\begin{aligned} &=\sqrt{(4-3)^2+(6-4)^2+(7-5)^2}\\ &=\sqrt{1^2+2^2+2^2}\\ &=\sqrt{1+4+4}\\ &=3 \end{aligned}

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Gurleen Kaur

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