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QJEEM23Ma5944: JEE Main 2023 Mathematics - Class 11 JEEM23Ma5944 Solution: The equations of the sides AB, BC and CA of a triangle ABC are…

The equations of the sides AB, BC and CA of a triangle ABC are : 2x+y=0,x+py=21a,(a±0) and x−y=3 respectively. Let P(2, a) be the centroid of ΔABC. Then (BC)2 is equal to ___________.

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JEE Main 2023 (Online) 24th January Evening Shift Mathematics - Straight Lines and Pair of Straight Lines Question 41 English Explanation

∵21a1−2p+1+3p+21ap+1=6

∴4p2−21ap+8p+42a−5=0...(1)

And −42a1−2p−2+21a−3p+1=3a\frac{-42 a}{1-2 p}-2+\frac{21 a-3}{p+1}=3 a

∴4p2−81ap+6ap2−24a+8p−5=0...(2)

From equation (1) - equation (2) we get;

60ap+66a−6ap2=0

∵a≠0⇒p2−10p−11=0p=−1 or 11⇒p=11.

When p=11p=11 then a=3a=3

Coordinate of B=(−3,6)B=(-3,6)

And coordinate of C=(8,5)C=(8,5)

∴BC2=122\therefore B C^{2}=122

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