Gauss-Jordan elimination on $$$\left[\begin{array}{ccc|c}1 & 1 & 1 & 4\\0 & -1 & 1 & 0\\-1 & 0 & 0 & -2\end{array}\right]$$$
Related calculators: Reduced Row Echelon Form (RREF) Calculator, Matrix Inverse Calculator
Your Input
Perform the Gauss-Jordan elimination on $$$\left[\begin{array}{ccc|c}1 & 1 & 1 & 4\\0 & -1 & 1 & 0\\-1 & 0 & 0 & -2\end{array}\right]$$$.
Solution
Add row $$$1$$$ to row $$$3$$$: $$$R_{3} = R_{3} + R_{1}$$$.
$$$\left[\begin{array}{ccc|c}1 & 1 & 1 & 4\\0 & -1 & 1 & 0\\0 & 1 & 1 & 2\end{array}\right]$$$
Add row $$$2$$$ to row $$$3$$$: $$$R_{3} = R_{3} + R_{2}$$$.
$$$\left[\begin{array}{ccc|c}1 & 1 & 1 & 4\\0 & -1 & 1 & 0\\0 & 0 & 2 & 2\end{array}\right]$$$
Answer
The reduced matrix is $$$\left[\begin{array}{ccc|c}1 & 1 & 1 & 4\\0 & -1 & 1 & 0\\0 & 0 & 2 & 2\end{array}\right]$$$A.