a=2i^−j^+k^
b=λj^+2k^ ; λ∈Z
c=a×b=(−2−λ)i^−4j^+2λk^
∣c∣=53
⇒5λ2+4λ−33=0
λ=2.2 or −3
⇒λ=−3
c=i^−4j^−6k^
let d=yj^+zk^
∣d∣=2
⇒y2+z2=4
(c⋅d)2=(4y+6z)2≤(42+62×y2+z2)2≤208
JEE Main 2026 — Mathematics Vectors & 3D Geometry
Let a=2i^−j^+k^ and b=λj^+2k^,λ∈Z be two vectors. Let c=a×b and d be a vector of magnitude 2 in yz-plane. If ∣c∣=53, then the maximum possible value of (c⋅d)2 is equal to :
Held on 22 Jan 2026 · Verified 6 Jul 2026.
26
52
208
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