Answer
$\begin{bmatrix}1& 4\\0 & -9 \end{bmatrix} $
Work Step by Step
We are given the matrix $\begin{bmatrix}1&4\\4&7\end{bmatrix}$.
Perform the row operation as: $R_2=-4R_1+R_2$
Therefore, we can write:
$\begin{bmatrix}1&4\\-4(1)+4 & -4(4)+7 \end{bmatrix} =\begin{bmatrix}1& 4\\0 & -9 \end{bmatrix} $