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Need solution for RD Sharma Maths Class 12 Chapter 22 Algera of Vectors Excercise 22.7 Question 5

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Answer:

Given position vectors are collinear for all the real values of  \lambda

Hint:

To be collinear, vectors must be a multiple of another.

Given:

\vec{a}, \vec{b}  Are non collinear vectors            .

Solution:

Let, position vectors of points X, Y and Z are  \vec{a}+\vec{b}, \vec{a}-\vec{b} \& \vec{a}+\lambda \vec{b}  respectively.

Then, \overrightarrow{XY}  Position of vector Y – Position of vector X

\begin{aligned} &=(\vec{a}-\vec{b})-(\vec{a}+\vec{b}) \\ & \end{aligned}

=-2 \vec{b}

Similarly

\overrightarrow{YZ}  Position of vector Z – Position of vector Y

\begin{aligned} &=(\vec{a}+\lambda \vec{b})-(\vec{a}-\vec{b})\\ \end{aligned}

=\lambda \vec{b}+\vec{b}\\

=\vec{b}(\lambda+1)       … (i)

Now,

\overrightarrow{Z X}  Position of vector X – Position of Z

\begin{aligned} &=(\vec{a}+\vec{b})-(\vec{a}+\lambda \vec{b}) \\ \end{aligned}

=\vec{b}-\lambda \vec{b} \\

=\vec{b}(1-\lambda) \\

=-\vec{b}(\lambda-1)                            …(ii)

From (i) and (ii)

\overrightarrow{Z X}=-K \overrightarrow{Y Z}

Here point Z is common

Thus, we can say that for all real values of  \lambda given position vectors are parallel

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