Practicing Success
If $\left|\begin{array}{rrr}-a^2 & a b & a c \\ a b & -b^2 & b c \\ a c & b c & -c^2\end{array}\right|=\lambda a^2 b^2 c^2$, then the value of $\lambda$ is : |
4 3 2 1 |
4 |
$\left|\begin{array}{rrr}-a^2 & a b & a c \\ a b & -b^2 & b c \\ a c & b c & -c^2\end{array}\right|=\lambda a^2 b^2 c^2$ taking factor a, b,c from R1, R2, R3 respectively (rows of matrix) so $a b c\left|\begin{array}{ccc}-a & b & c \\ a & -b & c \\ a & b & -c\end{array}\right|=\lambda a^2 b^2 c^2$ taking out factor a, b, c from C1, C2, C3 respectively (Columns of matrix) $\Rightarrow a^2 b^2 c^2\left|\begin{array}{ccc}-1 & 1 & 1 \\ 1 & -1 & 1 \\ 1 & 1 & -1\end{array}\right|=\lambda a^2 b^2 c^2$ $\Rightarrow \lambda = \left|\begin{array}{ccc}-1 & 1 & 1 \\ 1 & -1 & 1 \\ 1 & 1 & -1\end{array}\right| \Rightarrow \lambda=\left|\begin{array}{rrr} using operations C2 → C1 + C2 C3 → C1 + C3 calculating determinant across R1 row $\lambda=-1\left|\begin{array}{ll}0 & 2 \\ 2 & 0\end{array}\right|+0+0=-1(-4)$ $\lambda = 4$ |