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Prove the Following Identities: ∣ ∣ ∣ ∣ a + X Y Z X a + Y Z X Y a + Z ∣ ∣ ∣ ∣ = a 2 ( a + X + Y + Z ) - Mathematics

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प्रश्न

Prove the following identity:

\[\begin{vmatrix}a + x & y & z \\ x & a + y & z \\ x & y & a + z\end{vmatrix} = a^2 \left( a + x + y + z \right)\]

 

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उत्तर

\[LHS\]

\[ = \begin{vmatrix}a + x & y & z \\ x & a + y & z \\ x & y & a + z\end{vmatrix}\]

\[ = \begin{vmatrix}a + x + y + z & y & z \\ a + x + y + z & a + y & z \\ a + x + y + z & y & a + z\end{vmatrix} \left[\text{ Applying }C_1 \text{ to }C_1 + C_2 + C_3 \right]\]

\[ = \left( a + x + y + z \right)\begin{vmatrix}1 & y & z \\ 1 & a + y & z \\ 1 & y & a + z\end{vmatrix} \left[\text{ Taking }\left( a + x + y + z \right)\text{ common from }C_1 \right]\]

\[ = \left( a + x + y + z \right)\begin{vmatrix}1 & y & z \\ 0 & a & 0 \\ 0 & 0 & a\end{vmatrix} \left[\text{ Applying }R_2 \text{ to } R_2 - R_1\text{ and }R_3 \text{ to }R_3 - R_1 \right]\]

\[ = \left( a + x + y + z \right) a^2 \left[\text{ Expanding along first column }\right]\]

\[ = a^2 \left( a + x + y + z \right)\]

\[ = RHS\]

\[ \therefore \begin{vmatrix}a + x & y & z \\ x & a + y & z \\ x & y & a + z\end{vmatrix} = a^2 \left( a + x + y + z \right)\]

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अध्याय 6: Determinants - Exercise 6.2 [पृष्ठ ६१]

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आरडी शर्मा Mathematics [English] Class 12
अध्याय 6 Determinants
Exercise 6.2 | Q 44 | पृष्ठ ६१

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