Question

The value of $x$, so that $\lceil 1x1\rceil \left[\begin{array}{ccc}1& 3& 2\\ 0& 5& 1\\ 0& 3& 2\end{array}\right]\left[\begin{array}{c}1\\ 1\\ x\end{array}\right]=0$ is

• A. $\frac{-7\pm \sqrt{35}}{2}$
• B. $\frac{-9\pm \sqrt{53}}{2}$
• C. $\pm 2$
• D. $\frac{-7}{10}$

Answer 1

The correct option is D $\frac{-7}{10}$

Consider, $\left[\begin{array}{ccc}1& x& 1\end{array}\right]\left[\begin{array}{ccc}1& 3& 2\\ 0& 5& 1\\ 0& 3& 2\end{array}\right]=1\left[\begin{array}{ccc}1& 3+5x+3& 5\end{array}\right]$

$\left[\begin{array}{ccc}1& 6+5x& 5\end{array}\right]\left[\begin{array}{c}1\\ 1\\ x\end{array}\right]=7+10x$

By given, we have

$7+10x=0$

$\Rightarrow x=-\frac{7}{10}$.