Question

The value of $a$ if $\left[\begin{array}{ccc}1& a& 1\end{array}\right]\left[\begin{array}{c}2a\\ a\\ 2\end{array}\right]=\left[\begin{array}{c}1\end{array}\right]$

• A. $1$
• B. $-1$
• C. $2$
• D. $-2$

Answer 1

The correct option is B $-1$

By matrix multiplication we have
$2a+a^2+2=1\Rightarrow (a+1{)}^2=0$
So $a=-1$