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JEE Advanced · Mathematics · 30. Vector Algebra

Let ΔPQR be a triangle. Let a= QR,  b= RP and c= PQ. If a=12, b=43 and b  c=24, then which of the following is (are) true ?

  1. A c22- a=12
  2. B c22- a=30
  3. C a × b+ c × a=483
  4. D a b= -72
Verified Solution

Answer & Solution

Correct Answer

(A) c22- a=12

Step-by-step Solution

Detailed explanation

a=12, b=43, b.c=24
a+b+c=0 (Sides of triangle)
b+c=-a
b+c.b+c=-a.-a
b2+c2+2b.c=a2
48+c2+2×24=122
c2=48
c22-a=482-12=12
c22+a=482+12=36
a×b+c×a=a×b-a×c
=a×b-c
a=-b-c
=-b-c×b-c=b-c×b+c
=2b×c
=2b2c2-b.c2=248×48-242
=2×244-1=483
a+b=-c
a+b.a+b=-c.-c
a2+b2+2a.b=c2
a.b=-a22=-1222=-72
From JEE Advanced
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