मराठी

(A) is Given by 1 3 X − 5 (B) is Given by X + 5 3 (C) Does Not Exist Because F is Not One-one (D) Does Not Exist Because F is Not onto

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प्रश्न

If \[f : R \to R is given by f\left( x \right) = 3x - 5, then f^{- 1} \left( x \right)\] 

 

पर्याय

  • is given by  \[\frac{1}{3x - 5}\]  

  • is given by \[\frac{x + 5}{3}\]

  • does not exist because f is not one-one

  • does not exist because f is not onto

MCQ
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उत्तर

Clearly, f is a bijection.
So, f -1 exists.

\[Let f^{- 1} \left( x \right) = y . . . \left( 1 \right)\] .....(1)
\[ \Rightarrow f\left( y \right) = x\] 
\[ \Rightarrow 3y - 5 = x\] 
\[ \Rightarrow 3y = x + 5\] 
\[ \Rightarrow y = \frac{x + 5}{3}\]  
\[ \Rightarrow f^{- 1} \left( x \right) = \frac{x + 5}{3} [\text{from}\left( 1 \right)]\]

So, the answer is (b).

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पाठ 2: Functions - Exercise 2.6 [पृष्ठ ७७]

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आर.डी. शर्मा Mathematics Volume 1 and 2 [English] Class 12
पाठ 2 Functions
Exercise 2.6 | Q 31 | पृष्ठ ७७

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