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BITSAT 2019
Exam
BITSAT
Year
2019
Subject
Mathematics
Chapter
Differentiation

BITSAT 2019 · Mathematics · Differentiation

Let f ( x ) = x [x], x Z , ( [ · ] denotes greatest integer...

Let f(x)=x[x],x∉Zf ( x ) = x \left[x\right], x \notin Z, ([⋅][ \cdot ] denotes greatest integer function), then f′(x)isequaltof^{'}\left(x\right) is equal to

Options

  1. A2x2x
  2. B[x]\left[x\right]
  3. C2[x]2 \left[x\right]
  4. D11

Correct answer

B. [x]\left[x\right]

Step-by-step solution

We have, f(x)=x[x]f ( x ) = x \left[x\right]

∴[x]∴ \left[x\right] is an integer.

⇒f(x)=px[∵[x]=p]⇒ f \left(x\right) = px \left[∵ [ x ] = p\right]

⇒f′(x)=p=[x]⇒ f^{'} \left(x\right) = p = \left[x\right]

∴f′(x)=[x]</p>∴ f^{'} \left(x\right) = \left[x\right]</p>

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