NIMCET 2014 — Mathematics PYQ
NIMCET | Mathematics | 2014Suppose the system of linear equations:
−2x+y+z=l
x−2y+z=m
x+y−2z=n
is such that l+m+n=0, then the system has:
Choose the correct answer:
- A.
A non-zero unique solution.
- B.
Trivial solution.
- C.
Infinitely many solutions.
(Correct Answer) - D.
No solution.
Infinitely many solutions.
Explanation
Solution
Concept:
-
Rouché–Capelli theorem: A system has a solution if rank(A)=rank(A∣B).
-
If n > \text{rank}(A) = \text{rank}(A|B), there are infinitely many solutions.
Calculation:
Augmented matrix [A∣B] is:
Applying R3→R1+R2+R3:
Since l+m+n=0, the last row becomes all zeros.
rank(A)=rank(A∣B)=2, which is less than the number of variables (3).
Therefore, the system has infinitely many solutions.
Correct Option: 3
Explanation
Solution
Concept:
-
Rouché–Capelli theorem: A system has a solution if rank(A)=rank(A∣B).
-
If n > \text{rank}(A) = \text{rank}(A|B), there are infinitely many solutions.
Calculation:
Augmented matrix [A∣B] is:
Applying R3→R1+R2+R3:
Since l+m+n=0, the last row becomes all zeros.
rank(A)=rank(A∣B)=2, which is less than the number of variables (3).
Therefore, the system has infinitely many solutions.
Correct Option: 3

