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# y=f(x)^-1 yeah...but which one? watch

1. Hi,

I was wondering if you find the inverse of y=2/x-1, wouldn't it be one of either:

2/x+1=y

or

2-x/x=y?

The top one is apparently wrong, I don't see how though. To me it is just another method with an alternative outcome!

Could anyone help me out? I'd really appreciate it!
2. (Original post by Alevelstudent123)
Hi,

I was wondering if you find the inverse of y=2/x-1, wouldn't it be one of either:

2/x+1=y

or

2-x/x=y?

The top one is apparently wrong, I don't see how though. To me it is just another method with an alternative outcome!

Could anyone help me out? I'd really appreciate it!

Do you mean or ?
3. (Original post by Alevelstudent123)
Hi,

I was wondering if you find the inverse of y=2/x-1, wouldn't it be one of either:

2/x+1=y

or

2-x/x=y?

The top one is apparently wrong, I don't see how though. To me it is just another method with an alternative outcome!

Could anyone help me out? I'd really appreciate it!
I'm going to assume that your equation is y=(2/x)-1, but it would be useful if you could make sure that you use brackets in future posts to avoid ambiguity. In this case, the inverse should be y=2/(x+1), as you suggest.

However, if you meant y=2/(x-1) as the original equation, then this has a different inverse.
4. if y=2/(x+1) Inverse (x/2)-1

if y=(2/x)+1 Inverse (x/2)-1/2
5. (Original post by victor_b1992)
if y=2/(x+1) then dy/dx 2/x +1

if y=(2/x)+1 then dy/dx 2x + 2
Have you read what the OP is actually asking for? Differentiation doesn't come into their question, and you've actually given incorrect derivatives anyway.
6. y=2/(x-1)
y(x-1)=2
yx-y=2
x=2+y/(y)
f^-1(x)=2+x/(x)
?
7. If the question should read y = (2/x)-1, then your answer is correct. If you mean 2/(x-1), then the answer would be different.

EDIT: See the above post.
8. (Original post by Illusionary)
Have you read what the OP is actually asking for? Differentiation doesn't come into their question, and you've actually given incorrect derivatives anyway.
sry i mean inverse
9. (Original post by victor_b1992)
sry i mean inverse
...but they're not correct as inverses, either.
10. (Original post by Illusionary)
...but they're not correct as inverses, either.
ok well it right nw lol just didn't no where my head was at this question lol.

Cross multiply, so that:

y(x - 1) = 2

yx - y = 2

yx = 2 + y

Re-writing:

So:

12. As a notational point (call me a pedant), this is , not , which is completely different.

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Updated: January 18, 2010
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