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JEE Main 2020
Matrices & Determinants
Matrices and Determinants
Medium

Question

If the system of linear equations, x + y + z = 6 x + 2y + 3z = 10 3x + 2y + λ\lambda z = μ\mu has more than two solutions, then μ\mu - λ\lambda 2 is equal to ______.

Answer: 2

Solution

Key Concept: Conditions for Solutions of a System of Linear Equations

For a system of linear equations in three variables, represented in matrix form as AX=BAX=B, where AA is the coefficient matrix, XX is the variable matrix, and BB is the constant matrix, we can use Cramer's Rule to determine the nature of its solutions.

Let Δ=det(A)\Delta = \det(A) be the determinant of the coefficient matrix. Let Δ1,Δ2,Δ3\Delta_1, \Delta_2, \Delta_3 be the determinants obtained by replacing the 1st, 2nd, and 3rd columns of AA respectively with the constant terms from matrix BB.

There are three possibilities for the solutions:

  1. Unique Solution: If

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