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JEE Main 20231 FebruaryEvening Shift
Exam
JEE Main
Year
2023
Date
1 February
Shift
Evening Shift
Subject
Mathematics
Chapter
Functions

JEE Main 2023 · 1 February · Evening Shift · Mathematics · Functions

Let f: R - \ 0, 1\ → R be a function such that f(x) + f((1)/(1 -...

Let f:R−{0,1}→Rf: R - \left\{0, 1\right\} \to R be a function such that f(x)+f(11−x)=1+xf\left(x\right) + f\left(\dfrac{1}{1 - x}\right) = 1 + x. Then f(2)f\left(2\right) is equal to :

Options

  1. A92\dfrac{9}{2}
  2. B94\dfrac{9}{4}
  3. C74\dfrac{7}{4}
  4. D73\dfrac{7}{3}

Correct answer

B. 94\dfrac{9}{4}

Step-by-step solution

Given,

f(x)+f(11−x)=1+xf\left(x\right) + f\left(\dfrac{1}{1 - x}\right) = 1 + x

x=2⇒f(2)+f(−1)=3…(1)x = 2 ⇒ f\left(2\right) + f\left(- 1\right) = 3 \ldots \left(1\right)

x=−1⇒f(−1)+fx = - 1 ⇒ f\left(- 1\right) + f\left(\dfrac{1}{2}\right) = 0 \ldots \left(2\right)</p><p></p><p>x = \dfrac{1}{2} ⇒ f\left(\dfrac{1}{2}\right) + f\left(2\right) = \dfrac{3}{2} \ldots \left(3\right)</p><p>Onsubtractingequation(3)andequation(2)</p><p>On subtracting equation \left(3\right) and equation \left(2\right) we get,

f(2)−f(−1)=34........(4)f ( 2 ) - f ( - 1 ) = \dfrac{3}{4} . . . . . . . . ( 4 )

On adding equation \left(1\right)andequation(4)and equation \left(4\right) we get,

2f(2)=922f\left(2\right) = \dfrac{9}{2}

⇒f(2)=94⇒ f\left(2\right) = \dfrac{9}{4}

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