Question Details

Let the function f be defined by f(x)=9+3x7−2x, then f-1(x) is

Options

A

9−3x/7+2x

B

7x−9/2x+3

C

2x−7/3x+9

D

2x−3/7x+9

Correct Answer :

7x−9/2x+3

Solution :

The correct option is 7x−9/2x+3.

To find the inverse function, denoted as f1(x), of the given function f(x), we follow a systematic algebraic procedure.

The original function is given by:
f(x)=9+3x72x

Step 1: Set the function equal to y.
We replace f(x) with y to work with standard variables:
y=9+3x72x

Step 2: Swap x and y.
To find the inverse function, we exchange the positions of x and y:
x=9+3y72y

Step 3: Solve the new equation for y.
First, we multiply both sides by the denominator (72y) to eliminate the fraction:
x(72y)=9+3y

Next, we expand the left side of the equation:
7x2xy=9+3y

To solve for y, we need to gather all terms containing y on one side of the equation, and all other terms on the opposite side. Let's add 2xy to both sides and subtract 9 from both sides:
7x9=3y+2xy

Now, we factor out y from the right-hand side:
7x9=y(3+2x)

Which is equivalent to:
7x9=y(2x+3)

Finally, we isolate y by dividing both sides by (2x+3):
y=7x92x+3

Therefore, the inverse function is:
f1(x)=7x92x+3

This matches the correct option 7x−9/2x+3.

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