How to find the rank and nullity of a matrix?
Understand the Problem
The question is asking for the methods to determine the rank and nullity of a matrix, which are fundamental concepts in linear algebra. The rank of a matrix is the dimension of the vector space generated by its rows or columns, while the nullity is the dimension of the kernel (or null space) of the matrix. Typically, this involves using techniques such as row reduction or applying the RankNullity Theorem.
Answer
Rank is found by counting nonzero rows in RREF, and nullity is calculated as $ \text{Nullity} = n  \text{Rank} $.
Answer for screen readers
The rank is determined by the number of nonzero rows in row echelon form, and the nullity can be found using the formula $ \text{Nullity} = n  \text{Rank} $.
Steps to Solve

Finding the Rank of the Matrix
To find the rank, we can use row reduction (Gaussian elimination) to bring the matrix into row echelon form (REF) or reduced row echelon form (RREF). Count the number of nonzero rows after the matrix has been reduced. This count will give you the rank. 
Determining the Nullity of the Matrix
According to the RankNullity Theorem, the sum of the rank and nullity of a matrix equals the number of its columns. The nullity can be calculated using the formula: $$ \text{Nullity} = n  \text{Rank} $$ where $n$ is the total number of columns in the matrix. 
Example Calculation
If we have a matrix with 4 columns and we found that the rank is 2:
 Use the nullity formula to find nullity:
$$ \text{Nullity} = 4  2 = 2 $$
Thus, the nullity is 2.
The rank is determined by the number of nonzero rows in row echelon form, and the nullity can be found using the formula $ \text{Nullity} = n  \text{Rank} $.
More Information
The rank of a matrix indicates the number of linearly independent vectors in the row or column space. The nullity reflects the number of solutions to the homogeneous equation associated with the matrix. These concepts are crucial in understanding the behavior of linear transformations represented by the matrix.
Tips
 Forgetting to apply row reduction correctly can lead to an incorrect count of nonzero rows, thus affecting the rank.
 Confusing the definitions of rank and nullity and applying the formulas incorrectly.