Target Exam

CUET

Subject

-- Applied Mathematics - Section B2

Chapter

Numbers, Quantification and Numerical Applications

Question:

If $A=R-\begin{Bmatrix}\frac{3}{2}\end{Bmatrix}$ and function $f: A→ A $ is defined by $f(x)=\frac{3x-2}{2x-3}$, then

Options:

$f^{-1}(x)=f(x)$

$f^{-1}(x)=-f(x)$

$fof(x)=-x$

$f^{-1}(x)=\frac{3x+2}{2x+3}$

Correct Answer:

$f^{-1}(x)=f(x)$

Explanation:

The correct answer is Option (1) → $f^{-1}(x)=f(x)$

$f(x)=\frac{3x-2}{2x-3},A=R-\left\{\frac{3}{2}\right\}$

Injectivity (One-to-one):

$⇒f(x_1)=f(x_2)$

$⇒\frac{3x_1-2}{2x_1-3}=\frac{3x_2-2}{2x_2-3}$

$⇒(3x_1-2)(3x_2-2)=(2x_1-3)(2x_2-3)$

$⇒-9x_1+4x_1=-9x_2+4x_2$

$⇒x_1=x_2$

∴ This is one-to-one function.

Surjectivity (Onto):

A function is onto if for every $y∈A$, there exists $x∈A$ such that $f(x)=y$.

$⇒y(2x-3)=3x-2$

$⇒x=\frac{3y-2}{2y-3}$

∴ f(x) is surjective.

and, $f(x)=f^{-1}(x)$