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GATE 2019 AE – Question 36

Engineering Mathematics · Linear Algebra: Vector algebra, matrix algebra, systems of linear equations, rank, eigenvalues and eigenvectors · 2 marks · Multiple choice

How many solutions does the homogeneous system 2x−y−z=0, −x+2y−z=0, −x−y+2z=0 have?

  1. No solution
  2. One unique solution
  3. Three solutions
  4. Infinitely many solutions

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Show answer and explanation

Correct answer: (D) Infinitely many solutions

Explanation

Subtracting equations gives x=y=z. Every vector (a,a,a), for arbitrary real a, satisfies all three equations. The matrix has rank two and one free parameter. Therefore infinitely many solutions, D; a homogeneous system always has at least its zero solution.

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