v=a×b=i^12j^−21k^3−1=−i^+7j^+5k^.
v⋅c=−λ+7+5=11⇒λ=1.
c=i^+j^+k^, ∣c∣=3.
b⋅c=2+1−1=2.
Projection p=∣c∣∣b⋅c∣=32.
9p2=9×34=12.
JEE Main 2026 — Mathematics Vectors & 3D Geometry
Let a=i^−2j^+3k^,b=2i^+j^−k^,c=λi^+j^+k^ and v=a×b. If v⋅c=11 and the length of the projection of b on c is p, then 9p2 is equal to
Held on 23 Jan 2026 · Verified 6 Jul 2026.
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