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Prove that the Following Vectors Are Non-coplanar: 3 ^ I + ^ J − ^ K , 2 ^ I − ^ J + 7 ^ K and 7 ^ I − ^ J + 23 ^ K - Mathematics

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Question

Prove that the following vectors are non-coplanar:

\[3 \hat{i} + \hat{j} - \hat{k} , 2 \hat{i} - \hat{j} + 7 \hat{k}\text{ and }7 \hat{i} - \hat{j} + 23 \hat{k}\]
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Solution

Let if possible the given vectors are coplanar. Then one of the given vector is expressible in terms of the other two.
We have,
\[3 \hat{i} + \hat{j} - \hat{k} = x(2 \hat{i} - \hat{j} + 7 \hat{k} ) + y(7 \hat{i} - \hat{j} + 23 \hat{k} ) . \]
\[ = \hat{i} (2x + 7y) + \hat{j} ( - x - y) + \hat{k} (7x + 23y) . \]
\[ \Rightarrow 2x + 7y = 3 , x + y = - 1, 7x + 23y = - 1 . \]
By solving the first two equations, we get
\[ \Rightarrow x = - 2, y = 1 .\]
Clearly these values of x and y does not satisfy the third equation.
Hence the given vectors are non-coplanar.

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Chapter 23: Algebra of Vectors - Exercise 23.8 [Page 65]

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RD Sharma Mathematics [English] Class 12
Chapter 23 Algebra of Vectors
Exercise 23.8 | Q 6.1 | Page 65

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