R2=P2+Q2+2PQcosθ 
4R2=P2+4Q2+4PQcosθ
4R2=P2+Q2−2PQcosθ
On(1)+(2),5R2=2P2+2Q2
On(3)×2+(2),12R2=3P2+6Q2
2P2+2Q2−5R2=0
3P2+6Q2−12R2=0
−24+30P2=24−15Q2=12−6R2 6P2=9Q2=6R2 or P2:Q2:R2=2:3:2
JEE Main 2003 — Mathematics Vectors & 3D Geometry
The resultant of forces P and Q is R. If Q is doubled then R is doubled. If the direction of Q is reversed, then R is again doubled. Then P2:Q2:R2 is
Held on 30 Apr 2003 · Verified 6 Jul 2026.
2:3:1
3:1:1
2:3:2
1:2:3
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