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QJEEM14Ma5ee4: JEE Main 2014 Mathematics - Class 12 JEEM14Ma5ee4 Solution: If is the inverse of a function and then is equal to:

If gg is the inverse of a function ff and f′(x)=11+x5,f'\left( x \right) = {1 \over {1 + {x^5}}}, then g′(x)g'\left( x \right) is equal to:

Multiple Choice Options

  • A 11+{g(x)}5{1 \over {1 + {{\left\{ {g\left( x \right)} \right\}}^5}}}
  • B 1+{g(x)}51 + {\left\{ {g\left( x \right)} \right\}^5}
  • C 1+x51 + {x^5}
  • D 5x45{x^4}

Step-by-Step Verified Solution

Since f(x)f(x) and g(x)g(x) are inverse of each other

∴\therefore g′(f(x))=1f′(x)g'\left( {f\left( x \right)} \right) = {1 \over {f'\left( x \right)}}

⇒g′(f(x))=1+x5\Rightarrow g'\left( {f\left( x \right)} \right) = 1 + {x^5}

( \left( \, \right. As  f′(x)=11+x5\,f'\left( x \right) = {1 \over {1 + {x^5}}}  )\left. \, \right)

Here x=g(y)x=g(y)

∴\therefore g′(y)=1+{g(y)}g'\left( y \right) = 1 + \left\{ {g\left( y \right)} \right\}

⇒g′(x)=1+{g(x)}\Rightarrow g'\left( x \right) = 1 + \left\{ {g\left( x \right)} \right\}

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