Question:

Let \(f,g,h\) be differentiable functions such that \[ \begin{vmatrix} f(x) & g(x) & h(x)\\ f'(x) & g'(x) & h'(x)\\ f''(x) & g''(x) & h''(x) \end{vmatrix} =0. \] Then which of the following statements is correct?

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For questions involving determinants of functions and their derivatives, immediately think of the Wronskian. A zero Wronskian is a strong indicator of linear dependence.
Updated On: Jun 10, 2026
  • \(f,g,h\) are always linearly independent
  • \(f,g,h\) are linearly dependent
  • Exactly two of them are equal
  • None of these
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The Correct Option is B

Solution and Explanation

Concept: The determinant \[ \begin{vmatrix} f & g & h\\ f' & g' & h'\\ f'' & g'' & h'' \end{vmatrix} \] is called the Wronskian of the functions \(f,g,h\). A vanishing Wronskian is one of the standard tests used to identify linear dependence among differentiable functions under appropriate conditions.

Step 1: Recall the definition of linear dependence Functions \(f,g,h\) are linearly dependent if there exist constants \(A,B,C\), not all zero, such that \[ Af(x)+Bg(x)+Ch(x)=0 \] for all \(x\) in the interval.

Step 2: Interpret the determinant The determinant given is \[ W(f,g,h)=0 \] where \(W\) denotes the Wronskian. A Wronskian identically equal to zero indicates that the functions fail to generate three independent directions in the function space. Thus they satisfy a non-trivial linear relation.

Step 3: Conclude Hence \[ f,g,h \] must be linearly dependent. Therefore, \[ \boxed{\text{\(f,g,h\) are linearly dependent}} \]
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