If A1,B1,C1.. are respectively the co-factor of the elements a1,b1,c1. △=∣∣
∣∣a1b1c1a2b2c2a3b3c3∣∣
∣∣, then ∣∣∣B2C2B3C3∣∣∣
A
a1△
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B
a1a3△
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C
(a1+b1)△
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D
Noneofthese
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Solution
The correct option is Aa1△ B2=a1c3−a3c1c2=−(a1b3−a3b1)B3=−(a1c2−a2c1)c3=a1b2−b1a2∣∣∣B2C2B3C3∣∣∣=∣∣∣a1c3−a3c1−a1b3+a3b1−a1c2+a2c1a1b2−b1a2∣∣∣=∣∣∣a1c3−a1b3−a1c2a1b2∣∣∣+∣∣∣a1c3a3b1−a1c2−a2b1∣∣∣+∣∣∣−a3c1−a1b3a2c1a1b2∣∣∣1∣∣∣−a3c1a3b1a2c1−a2b1∣∣∣=a21∣∣∣c3−b3−c2b2∣∣∣+a1b1∣∣∣c3a3−c2−a2∣∣∣+a1c∣∣∣−a3−b3a2b2∣∣∣+b1c1∣∣∣−a3a3a2−a2∣∣∣=a1{a1(b2c3−b3c2)−b1(a2c3−a3c2)+c1(a2b3−a3b2)}=a1∣∣
∣∣a1b1c1a2b2c2a3b3c3∣∣
∣∣=a1Δ