How do you get this?:)
let f(x)=(x+2)/(x+8)
f^-1(-9)=?

Question

How do you get this?:)
let f(x)=(x+2)/(x+8) 
f^-1(-9)=?

amistre64 · Answer

you want the inverse of f(x)

anonymous · Answer

$$f^(-1)(x) = -(2 (4 x-1))/(x-1)$$

amistre64 · Answer

the inverse is gotten suslly by switching x and y and resolves for y

anonymous · Answer

You don't have to find the inverse, Just plug f(x)=-9, and then solve for x. That value of x is the inverse at x=-9.

anonymous · Answer

let y = x+2 / x+8
yx + 8y = x+2
x(1-y) = 8y-2
x = (8y-2)/1-y
which gives u d inverse
now switch x and y
and put in d value of x to get y

anonymous · Answer

thank you!:)

amistre64 · Answer

x=(y+2)/(y+8)

x(y+8)=y+2

xy +8x = y+2

xy - y = -8x +2

y(x-1) = -8x+2

y = (-8x+2)
       -------
         (x-1)

amistre64 · Answer

y = (-8(-9)+2)/(-9-1)

y = 74/-10 = -7.4

anonymous · Answer

welll i did the very same

amistre64 · Answer

yay!!  its verified then ;)

anonymous · Answer

A simpler method, is to plug f(x)=-9 and then solve for x:
$$-9={x+2 \over x+8} \implies -9x-72=x+2 \implies 10x=-74 \implies x=- 7.4$$
So,$$f^{-1}(-9)=-7.4$$

anonymous · Answer

I like my method :P

amistre64 · Answer

your method is just the same method rehashed lol

anonymous · Answer

Haha, not really.

anonymous · Answer

admit it, mine is better :P