Question Details

Let f: R – {3/5} → R be defined by f(x) = 3x+2/5x−3 then

Options

A

f⁻¹(x) = f(x)

B

f⁻¹(x) = -f(x)

C

(f o f)x = -x

D

f⁻¹(x) = 1/19 * f(x)

Correct Answer :

f⁻¹(x) = f(x)

Solution :

The correct option is f⁻¹(x) = f(x).

To understand why this is correct, let us find the inverse of the function f(x) step-by-step.
The given function is defined as:
f ( x ) = 3 x + 2 5 x 3

Let y=f(x). To find the inverse function f1(x), we need to express x in terms of y:
y = 3 x + 2 5 x 3

Multiply both sides by (5x3) to clear the denominator:
y ( 5 x 3 ) = 3 x + 2

Expand the left side of the equation:
5 x y 3 y = 3 x + 2

Rearrange the terms to group all terms containing x on one side:
5 x y 3 x = 3 y + 2

Factor out x from the left-hand side:
x ( 5 y 3 ) = 3 y + 2

Divide both sides by (5y3) to solve for x:
x = 3 y + 2 5 y 3

Since y=f(x) implies x=f1(y), we have:
f 1 ( y ) = 3 y + 2 5 y 3

Replacing the dummy variable y with x, we get the inverse function:
f 1 ( x ) = 3 x + 2 5 x 3

Comparing this expression with the original function, we observe that:
f 1 ( x ) = f ( x )

Therefore, the inverse of the function is identical to the function itself.

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