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Question #75847

Difficulty: 8/10 | 🟢 Free

The Question

Let u⃗1=({x},{y},{z})\vec{u}_1 = (\{x\}, \{y\}, \{z\}), u⃗2=({y},{z},{x})\vec{u}_2 = (\{y\}, \{z\}, \{x\}), u⃗3=({z},{x},{y})\vec{u}_3 = (\{z\}, \{x\}, \{y\}) and v⃗1=([x],[y],[z])\vec{v}_1 = ([x], [y], [z]), v⃗2=([y],[z],[x])\vec{v}_2 = ([y], [z], [x]), v⃗3=([z],[x],[y])\vec{v}_3 = ([z], [x], [y]). Let w⃗1=i^,w⃗2=j^,w⃗3=k^\vec{w}_1 = \hat{i}, \vec{w}_2 = \hat{j}, \vec{w}_3 = \hat{k} and x⃗1=j^,x⃗2=k^,x⃗3=i^\vec{x}_1 = \hat{j}, \vec{x}_2 = \hat{k}, \vec{x}_3 = \hat{i}. A 3×33 \times 3 matrix MM is defined by its entries Mij=(u⃗i⋅w⃗j)(v⃗i⋅x⃗j)−(u⃗i⋅x⃗j)(v⃗i⋅w⃗j)M_{ij} = (\vec{u}_i \cdot \vec{w}_j)(\vec{v}_i \cdot \vec{x}_j) - (\vec{u}_i \cdot \vec{x}_j)(\vec{v}_i \cdot \vec{w}_j). If x,y,zx, y, z form an arithmetic progression with a non-zero common difference, and [x],[y],[z][x], [y], [z] also form an arithmetic progression, find det⁡(M)\det(M).

Options

  • A.

    0

  • B.

    1

  • C.

    x+y+z

  • D.

    xyz

Check Your Answer

Correct Answer

Step-by-Step Solution

Explanation

How the Examiner Thinks

Monster

Ultra-high difficulty questions designed to test your limit, stamina, and deep conceptual understanding.

Concepts Behind This Question

Lagrange Identity|Linear Dependency of Rows|Integral Part and Fractional Part

Why This Question Is Tricky

Examiner Levers

Variable Manipulation

Algebraic solutions only (No numbers); tests pure symbolic logic.

Difficulty Boost : +4

Common Mistakes

The problem disguises a determinant of cross products using the expanded form of the Lagrange Identity.

The core trap lies in evaluating the sum of the cyclic components U+V+W, which forms a determinant involving fractional and integer parts.

Students often fail to recombine {t} + [t] = t within the determinant to expose the linear dependency caused by the Arithmetic Progression condition, missing that the matrix becomes singular.

Quick Facts About This Question

Question Information

SubjectMathematics
ChapterVector Algebra - Class 12
ConceptLagrange Identity
Difficulty8
Cognitive Load7
Target Solve Time160 sec
AccessFree