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+11 votes

Consider the following system of linear equations : $$2x_1 - x_2 + 3x_3 = 1$$ $$3x_1 + 2x_2 + 5x_3 = 2$$ $$-x_1+4x_2+x_3 = 3$$ The system of equations has

  1. no solution
  2. a unique solution
  3. more than one but a finite number of solutions
  4. an infinite number of solutions
in Linear Algebra by Boss (17.5k points) | 1.4k views

2 Answers

+21 votes
Best answer
rank of matrix $=$ rank of augmented matrix $=$ no of unknown $=$ $3$
so unique solution..

Correct Answer: $B$
by Veteran (60.9k points)
edited by
Can case C arise? If Yes, how shall we determine?

when rank of matrix = rank of augmented matrixno of unknown 

then it is infinite solutions. r < n, that is option D. I'm asking about option C
i think more than one but a finite number of solutions will never arise

as we have only 3 cases r=n,r<n and r>n
yes c option case can never arise

@Angkit   rank(r)>n  this case will never arise

+7 votes

Determinant of matrix =14 which is non zero

If The determinant of the coefficient matrix is non zero then definitely the system of given equation has a unique solution 

 so option B

by Boss (11.7k points)
in matrix $[A]_{3\times3},$ if $|A|_{3\times3}\neq0$ then rank should be $3$
if we get |A|=0 then we have to check for either infinite solⁿ or no solution we have to go with our fundamental method..

Then i think finding determinant is not fruitful

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