Question
If a,b and care non zero numbers, then Δ=∣∣
∣
∣∣b2c2bcb+cc2a2cac+aa2b2aba+b∣∣
∣
∣∣ is equal to
∣
∣∣b2c2bcb+cc2a2cac+aa2b2aba+b∣∣
∣
∣∣ is equal to
Answer: Option D
:
D
Multiplying R1 by a,R2 by b and R3 by c, we have
Δ=1abc∣∣
∣
∣∣ab2c2abcab+aca2bc2abcbc+aba2b2cabcac+bc∣∣
∣
∣∣=a2b2c2abc∣∣
∣∣bc1ab+acac1bc+abab1ac+bc∣∣
∣∣=abc∣∣
∣
∣∣bc1∑abac1∑abab1∑ab∣∣
∣
∣∣{byC3→C3+C1}=abc.∑ab∣∣
∣∣bc11ca11ab11∣∣
∣∣=0,[SinceC2≡C3].
Trick : Put a=1, b=2, c=3 and check it.
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:
D
Multiplying R1 by a,R2 by b and R3 by c, we have
Δ=1abc∣∣
∣
∣∣ab2c2abcab+aca2bc2abcbc+aba2b2cabcac+bc∣∣
∣
∣∣=a2b2c2abc∣∣
∣∣bc1ab+acac1bc+abab1ac+bc∣∣
∣∣=abc∣∣
∣
∣∣bc1∑abac1∑abab1∑ab∣∣
∣
∣∣{byC3→C3+C1}=abc.∑ab∣∣
∣∣bc11ca11ab11∣∣
∣∣=0,[SinceC2≡C3].
Trick : Put a=1, b=2, c=3 and check it.
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