Target Exam

CUET

Subject

-- Applied Mathematics - Section B2

Chapter

Algebra

Question:

If $A =\begin{bmatrix}5&1\\-2&0\end{bmatrix}$ and $B^T=\begin{bmatrix}1&10\\-2&-1\end{bmatrix}$, then the matrix AB is:

Options:

$\begin{bmatrix}1&10\\-1&0\end{bmatrix}$

$\begin{bmatrix}15&-11\\-2&4\end{bmatrix}$

$\begin{bmatrix}3&49\\-2&-20\end{bmatrix}$

$\begin{bmatrix}1&9\\-2&-20\end{bmatrix}$

Correct Answer:

$\begin{bmatrix}15&-11\\-2&4\end{bmatrix}$

Explanation:

The correct answer is Option (2) → $\begin{bmatrix}15&-11\\-2&4\end{bmatrix}$

$A =\begin{bmatrix}5&1\\-2&0\end{bmatrix}$

$B^T=\begin{bmatrix}1&10\\-2&-1\end{bmatrix}$

$⇒B=\begin{bmatrix}1&-2\\10&-1\end{bmatrix}$

$AB=\begin{bmatrix}5&1\\-2&0\end{bmatrix}\begin{bmatrix}1&-2\\10&-1\end{bmatrix}$

$=\begin{bmatrix}15&-11\\-2&4\end{bmatrix}$