Matrices & Determinants
Properties of determinants
Grade Class 12

Question:

If a<sup>2</sup> + b<sup>2</sup> + c<sup>2</sup> = -2 and f(x) = <math xmlns="http://www.w3.org/1998/Math/MathML"><mfenced open="|"><mtable><mtr><mtd><mn>1</mn><mo>+</mo><msup><mi>a</mi><mn>2</mn></msup><mi>x</mi></mtd><mtd><mo>(</mo><mn>1</mn><mo>+</mo><msup><mi>b</mi><mn>2</mn></msup><mo>)</mo><mi>x</mi></mtd><mtd><mo>(</mo><mn>1</mn><mo>+</mo><msup><mi>c</mi><mn>2</mn></msup><mo>)</mo><mi>x</mi></mtd></mtr><mtr><mtd><mo>(</mo><mn>1</mn><mo>+</mo><msup><mi>a</mi><mn>2</mn></msup><mo>)</mo><mi>x</mi></mtd><mtd><mn>1</mn><mo>+</mo><msup><mi>b</mi><mn>2</mn></msup><mi>x</mi></mtd><mtd><mo>(</mo><mn>1</mn><mo>+</mo><msup><mi>c</mi><mn>2</mn></msup><mo>)</mo><mi>x</mi></mtd></mtr><mtr><mtd><mo>(</mo><mn>1</mn><mo>+</mo><msup><mi>a</mi><mn>2</mn></msup><mo>)</mo><mi>x</mi></mtd><mtd><mo>(</mo><mn>1</mn><mo>+</mo><msup><mi>b</mi><mn>2</mn></msup><mo>)</mo><mi>x</mi></mtd><mtd><mn>1</mn><mo>+</mo><msup><mi>c</mi><mn>2</mn></msup><mi>x</mi></mtd></mtr></mtable></mfenced></math> then f(x) is a polynomial of degree-
(A) 0
(B) 1
(C) 2
(D) 3

Step-by-Step Solution

Key Concept: The determinant can be expressed as a product of two matrices or simplified using row/column operations. Given the condition a^2 + b^2 + c^2 = -2, the determinant simplifies to a constant value, making it a polynomial of degree 0.
Given the determinant, performing row operations R1 -> R1 - R2 and R2 -> R2 - R3, or observing the structure, one can show that the terms involving x cancel out or simplify significantly. Given a^2 + b^2 + c^2 = -2, the determinant evaluates to a constant independent of x.
Correct Answer: 1

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