If $(x-i y)(3+5 i)$ is the conjugate of $-6-24 i$ (where $x, y \in R$ and $i=\sqrt{-1})$, then the value of…

If $(x-i y)(3+5 i)$ is the conjugate of $-6-24 i$ (where $x, y \in R$ and $i=\sqrt{-1})$, then the value of $x$ and $y$ are respectively
  1. 5,3
  2. $5,-3$
  3. $-3,3$
  4. $3,-3$

Solution

$\begin{aligned} & (x-i y)(3+5 i)=-6+24 i \\ & \Rightarrow(3 x+5 y)+(5 x+3 y) i=-6+24 i \\ & \Rightarrow 3 x+5 y=-6 \text { and } 5 x-3 y=24\end{aligned}$ Solving we get $x=3$ and $y=-3$

Asked in: MHT CET 2022 (05 Aug Shift 2)

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