The value of $\begin{vmatrix} a+ib & c+id\\-c+id & a-ib\end{vmatrix}$ is :
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → $a^2+b^2+d^2+c^2$
$\begin{vmatrix} a+ib & c+id\\-c+id & a-ib\end{vmatrix}$
$=(a+ib)(a-ib)-(c+id)(-c+id)$
$=a^2+b^2+d^2+c^2$