Q : 6          Using the property of determinants and without expanding, prove that     

                  \begin{vmatrix} 0 &a &-b \\-a &0 & -c\\b &c &0 \end{vmatrix}=0

Answers (1)

We have given determinant

 \triangle = \begin{vmatrix} 0 &a &-b \\-a &0 & -c\\b &c &0 \end{vmatrix}

Applying transformation, \dpi{100} R_{1} \rightarrow cR_{1} we have then,

\triangle = \frac{1}{c}\begin{vmatrix} 0 &ac &-bc \\-a &0 & -c\\b &c &0 \end{vmatrix}

We can make the first row identical to the third row so,

Taking another row transformation: R_{1} \rightarrow R_{1}-bR_{2} we have,

\triangle = \frac{1}{c}\begin{vmatrix} ab &ac &0 \\-a &0 & -c\\b &c &0 \end{vmatrix} = \frac{a}{c} \begin{vmatrix} b &c &0 \\-a &0 & -c\\b &c &0 \end{vmatrix}

So, determinant has two rows R_{1}\ and\ R_{3} identical.

Hence \triangle = 0.

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