The correct option is D Δ1=Δ
△=∣∣
∣
∣∣Axx21Byy21Czz21∣∣
∣
∣∣
△1=∣∣
∣∣ABCxyzzyzxxy∣∣
∣∣
C1→xC1,C2→yC2,C3→zC3
△1=1xyz∣∣
∣
∣∣AxByCzx2y2z2xyzxyzxyz∣∣
∣
∣∣
|A|=∣∣AT∣∣
∴△1=1xyz∣∣
∣
∣∣Axx2xyzByy2xyzCzz2xyz∣∣
∣
∣∣
C3→C3/xyz
△1=xyzxyz∣∣
∣
∣∣Axx21Byy21Czz21∣∣
∣
∣∣
△1=∣∣
∣
∣∣Axx21Byy21Czz21∣∣
∣
∣∣
△1=△