Write out the original matrix M, draw a vertical line to the right of it, and then write the identity matrix to the right of that. You should now have what appears to be a matrix with three rows of six columns each. Recall that the identity matrix is a special matrix with 1s in each position of the main diagonal from upper left to lower right, and 0s in all other positions. For a review of the identity matrix and its properties, see Understand the Basics of Matrices. Your objective is to create the identity matrix on the left side of this newly augmented matrix. As you perform row reduction steps on the left, you must consistently perform the same operations on the right, which began as your identity matrix. Remember that row reductions are performed as a combination of scalar multiplication and row addition or subtraction, in order to isolate individual terms of the matrix. For a more complete review, see Row-Reduce Matrices. Keep repeating linear row reduction operations until the left side of your augmented matrix displays the identity matrix (diagonal of 1s, with other terms 0). When you have reached this point, the right side of your vertical divider will be the inverse of your original matrix. Copy the elements now appearing on the right side of the vertical divider as the inverse matrix.

TL;DR in Vietnamese:
Thêm ma trận đơn vị vào ma trận gốc. Thực hiện phép giảm hàng tuyến tính. Tiếp tục cho đến khi hình thành được ma trận đơn vị. Viết lại ma trận nghịch đảo.