Question

If f(x) and f-1(x) are inverse functions of each other and f(x)=2x+5 what is f-1(8)??

1. -1
2. 3/2
3. 41/8
4. 23

Answer 1

`f(x) = 2x + 5`

`x =2 {f}^( - 1) (x) + 5`

`2 {f}^( - 1) (x) = x - 5`

`{f}^( - 1) (x) = (1)/(2) (x - 5)`

`{f}^( - 1) (8) = (1)/(2) (8 - 5) = (3)/(2)`

Choice 2 is correct.

Answer 2

To find f-1(8), we need to determine the input value of x that would give us an output of 8 when the function f(x) = 2x + 5 is used. The solution is x = 3/2.

Step-by-step explanation:

To find f-1(8), we need to determine the input value of x that would give us an output of 8 when the function f(x) = 2x + 5 is used.

First, we can rewrite the function as y = 2x + 5.

Then, we substitute y with 8 and solve for x:

8 = 2x + 5

Next, subtract 5 from both sides:

3 = 2x

Finally, divide both sides by 2 to isolate x:

x = 3/2

Therefore, f-1(8) = 3/2.