In Chapter 7, RS Aggarwal from class 12 math tells the students about four different theorems. These theorems help the students understand the main ideas of the chapter better. Here is a list of the four theorems: 1. First theorem: If A is any n-by-n square matrix, then A (Adj A) is the same as (Adj A) A, which is the same as A I, where I is the n-by-n identity matrix. 2. Theorem 2: If A and B are both non-singular matrices of the same order, then AB and BA are also of the same order. 3. Theorem 3: If A and B are both square matrices of the same order, then the determinant of their product is equal to the product of their determinants, i.e., IAI IBI = AB 4. Theorem 4: If A is not singular, then A is also a square matrix that can be turned into a singular matrix.