Question

Please help hard math will medal!
Which pair of functions is not a pair of inverse functions?
A. f(x) = x+1/6 and g(x) = 6x-1
B. f(x) = x-4/19 and g(x) = 19x+4
C. f(x) = x^5 and g(x) = 5(sqrt)x
D. f(x) = x/x+20 and g(x) = 20/x-1

It's hard I'm thinking its D though?

Answer 1

You could either find the inverse of each given function f(x), OR, alternatively,

substitute function g(x) in each case for x within f(x) and determine whether the end result is x. If yes, the 2 functions are inverses of one another; otherwise, they are not.

Answer 2

Example: "C. f(x) = x^5 and g(x) = 5(sqrt)x"

In f(x)=x^5, replace x with 5sqrt(x):

f(g(x)) = (5sqrt(x))^5 \[=5^5 * (\sqrt{x})^5\]

Answer 3

Is this result = to x? If yes, f and g are inverse functions; if not, f and g are not inverses.

Answer 4

Do the same thing with D. Replace "x" in f(x) with g(x)=20 / (x-1). Is the result x? or not x?

Answer 5

so... do as mathmale indicated, and you'll see which one is it

Answer 6

20/x ? So d?

Answer 7

@mathmale

Answer 8

what did you get for the inverse of D?

Answer 9

I need to see how you've settled on option D.

Which method did you use: finding the inverse of the first function, or substituting the 2nd function for "x" in the first function?

Answer 10

I used math way lol this stuff is confusing

Answer 11

So I'm guessing it's not d

Answer 12

well... hmmm have you covered Inverse Functions yet?

I mean, do you know how to get the inverse of a function? as mathmale stated above

Answer 13

as far as mathway
well, if your instructions for the exercise is
use a calculator, and transcribe over whatever the calculator says
then that's ok

now, if you're supposed to do it, then I'd go with mathmale's way
or even check your book, it should have how to get the inverse of a function

Answer 14

It says NOT a pair, so would it be D?

Answer 15

well... we dunno what the inverse of D is though

Answer 16

so... get the inverse, see what you get
maybe the one there IS the inverse, who knows

Answer 17

D=-x

Answer 18

well, the inverse of x/(x+20) is not -x
so. recheck your inverse

Answer 19

I made a typo on d
It's 20x over x-1