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JEE Main 2021
Matrices & Determinants
Matrices and Determinants
Easy

Question

Let A and B be two 3 ×\times 3 real matrices such that (A 2 - B 2 ) is invertible matrix. If A 5 = B 5 and A 3 B 2 = A 2 B 3 , then the value of the determinant of the matrix A 3 + B 3 is equal to :

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Solution

This problem delves into the properties of matrices, specifically focusing on factorization and the implications of invertibility. The core idea is to cleverly manipulate the given matrix equations to isolate the term (A3+B3)(A^3 + B^3) and utilize the information about the invertibility of (A2B2)(A^2 - B^2).


1. Key Concept: Matrix Invertibility and Factorization

A matrix MM is invertible if and only if its determinant det(M)0\det(M) \ne 0. If MM is invertible, then for any matrix XX, the equation MX=0MX = 0 implies X=0X = 0 (by multiplying by M1M^{-1} on the left). Similarly, XM=0XM = 0 implies X=0X = 0. This property

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