Q170 / 270 · NDA 2018 (Phase 2) · Mathematics

What should be the value of $x$ so that the matrix $\left(\begin{array}{ll}2 & 4 \\ -8 & x\end{array}\right)$ does not have an inverse?

A
16
Correct answer
B
-16
C
8
D
-8

Solution

A matrix does not have an inverse if $|\mathrm{A}|=0$ $\left|\begin{array}{cc}2 & 4 \\ -8 & x\end{array}\right|=0 \Rightarrow x=-16$

Hence, the correct answer is option: 'B'.

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