logo

Ask Questions, Get Answers

 
X
 Search
Want to ask us a question? Click here
Browse Questions
Ad
0 votes

If $A$=$\begin{bmatrix} 2 & 1 \\3 & 4 \end{bmatrix}$, than (adj $A)A$=

\[\begin{array} {1 1}(1) \begin{bmatrix} \frac{1}{5}& 0 \\0 &\frac{1}{5} \end{bmatrix}& (2)\begin{bmatrix} 1 & 0 \\0 & 1 \end{bmatrix}\\ (3)\begin{bmatrix} 5 & 0 \\0 & -5 \end{bmatrix}& (4)\begin{bmatrix} 5 & 0 \\0 & 5 \end{bmatrix}\end{array}\]

Can you answer this question?
 
 

1 Answer

0 votes
$A$=$\begin{bmatrix} 2 & 1 \\3 & 4 \end{bmatrix}$
$(adj A) A = |A| I_2$
$|A|= \begin{vmatrix} 2 & 1 \\3 & 4 \end{vmatrix}$
$\qquad= 8-3=5 \neq 0$
$(adj \;A )A =5\begin{bmatrix} 1 & 0 \\ 0 & 1 \end{bmatrix}$
$=\begin{bmatrix} 5 & 0 \\0 & -5 \end{bmatrix}$
Hence 4 is the correct answer.
answered May 2, 2014 by meena.p
 

Related questions

Ask Question
student study plans
x
JEE MAIN, CBSE, NEET Mobile and Tablet App
The ultimate mobile app to help you crack your examinations
Get the Android App
...