Posted by **Millers** on Monday, October 14, 2013 at 3:06pm.

Find a formula for the inverse of the function. f(x) = (1 + 9x) / (8 - 4x)

- Calculus -
**Reiny**, Monday, October 14, 2013 at 3:29pm
let y = (1+9x)/(8-4x)

for inverse, interchange the x and y variables

x = (1+9y)/(8-4y)

now solve this for y .....

8x - 4xy = 1 + 9y

8x - 1 = 9y + 4xy

y(9+4x) = 8x-1

y = (8x-1)/(9+4x)

or

**f^-1 (x) = (8x-1)/(9+4x)**

check with some arbitrary x

say x = -1

f(-1) = (1-9)/(8+4) = -8/12 = -2/3

f^-1 (-2/3)

= (8(-2/3) - 1)/(9 + 4(-2/3))

= (-19/3) / (19/3)

= -1 , as expected

"more than likely" my answer is correct.

## Answer this Question

## Related Questions

- Calculus Help - The formula C =5/9(F − 32), where F ≥ −459.67...
- Pre-calculus - Given the following values for f(t): t : f(t) 3 : -7 6 : 6 9 : 19...
- math - The cost of producing q articles is given by the function C=f(q)=100+2q...
- calculus - f(x) = (x+2)/(x+6) What is f^(-1)(-6)? (what is f inverse of -6) I ...
- pre calculus - Find the inverse of the function below. Graph the function below ...
- Calculus - Given the function" f(x)=1/4x− 3, find a formula for the ...
- calculus - Find a formula for the inverse of the function f(x) = (4 x-1)/(2x+3)
- Pre-Calculus - Find the inverse function for the function f(x)=2^(x)+1/2^(x)-1 ...
- Algebra - Dan works at a hardware store. The employee discount is determined by ...
- math - Could you show me step by step how to find the inverse of this problem: ...

More Related Questions