Question

Given f(x) = (x - 7)/3, solve for f-1(4).
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Answer 1

write this as:

y = (x-7)/3

now rearrange this to get x in terms of y - what do you get?

Answer 2

x = (y - 7)/3?

Answer 3

that is not correct

Answer 4

you don't just swap the x and y

Answer 5

we start with: y = (x-7)/3

first multiply both sides by 3 - what do you get?

Answer 6

3y = (x-7)?

Answer 7

correct - now you can remove the braces to get: 3y = x - 7

next add 7 to both sides - what do you get?

Answer 8

10y =x

Answer 9

not quite you seem to have added 7y to the 3y instead of just adding 7 to it - try again

Answer 10

7 + 3y = x?

Answer 11

thats right - well done! :)

now we swap the two sides to get: x = 7 + 3y

final step is to swap the x and y variables to get the inverse function: y = 7 + 3x

Answer 12

now just plug x=4 into this

Answer 13

you just need to solve \(\large 4=\frac{x-7}{3}\)

Answer 14

the x value that you get is f inverse of (4)

Answer 15

it is the same thing
it's just that getting inverse first then evaluate it at 4 takes a longer route
than just solving for that equation which you get the answer quicker

Answer 16

@undeadknight26 - you need to use the method that you have been taught in class

Answer 17

:) of course use what you are taught!
but once you master it be open to other ways of doing things