If $\begin{bmatrix}x-1 & y-2 & z-3\\3 & u-4 & v-5\\8 & -4 & w-6\end{bmatrix}$ is skew symmetric matrix, then xu + yv + zw is:

-9 -15 -21 -35

-35

For skew - symmetric matrix diagonal element must be zero ∴ x = 1, u = 4, w = 6 and non diagonal element must be of opposite sign. ∴ y - 2 = -3, z - 3 = -8, v - 5 = 4 ∴ y = -1, z = -5, v = 9 xu + yv + zw = (1)(4) + (-1)(9) + (-5)(6) = 4 - 9 - 30 = -35