Year 12s: what will be the first way you research your future options? >>

C3 Functions

HensM

Can anyone help me find the inverse function for
f(x)=(x+2)/(x-1)
Thanks

Reply 1

Bruhh

I believe it doesn't have an inverse as the graph is symmetrical in the line y=x.

Reply 2

Kevin De Bruyne

Original post by HensM

Can anyone help me find the inverse function for
f(x)=(x+2)/(x-1)
Thanks

Remember that you want to make x the subject of the formula, so how do you do that?

Reply 3

HensM

Original post by SeanFM

Remember that you want to make x the subject of the formula, so how do you do that?

i know that it then changes to

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

and you have to rearrange, i can get to the point

x(y-1)=y+2
and then
xy-x=y+2

but i am unsure how to rearrange from this point

Reply 4

Kevin De Bruyne

Original post by HensM

i know that it then changes to

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

and you have to rearrange, i can get to the point

x(y-1)=y+2
and then
xy-x=y+2

but i am unsure how to rearrange from this point

Well done, you've got the idea :smile:

I would suggest getting anything with a y involved on one side, and anything without on the other side, and it may become a bit clearer then.

Reply 5

HensM

Original post by SeanFM

Well done, you've got the idea :smile:

I would suggest getting anything with a y involved on one side, and anything without on the other side, and it may become a bit clearer then.

Thats the help I'm looking for, i can't seem to finish rearranging

Reply 6

Kevin De Bruyne

Original post by HensM

Thats the help I'm looking for, i can't seem to finish rearranging

If you did what I suggested then you would end up with xy-y=x+2. There is something you can do to get y on it's own on the left hand side. What do you think?

Reply 7

HensM

Original post by SeanFM

If you did what I suggested then you would end up with xy-y=x+2. There is something you can do to get y on it's own on the left hand side. What do you think?

dividing out by x would give you
y-y=(x+2)/x

which can't be right, as y-y would = 0

Reply 8

Kevin De Bruyne

Original post by HensM

dividing out by x would give you
y-y=(x+2)/x

which can't be right, as y-y would = 0

Dividing by x would give you y-(y/x) = (x+2)/x.

Going back to xy-y=x+2 - is there a common factor between the two terms on the left hand side? If so, what is it?

Reply 9

HensM

Original post by SeanFM

Dividing by x would give you y-(y/x) = (x+2)/x.

Going back to xy-y=x+2 - is there a common factor between the two terms on the left hand side? If so, what is it?