F(x)=... Help please.

bmi92 · 18 Jan 2010 at 20:20

Hey guys,

Revising for my C3 math exam on Wednesday and came across this question, It seems fairly simple but can't get my head around it.

i) F(x)= X+1/X-1

Show that FF(x)= X

ii) Hence write down F^-1 (x). What can you deduce about the symmetry of the curve y=f^-1(x)?

Help please guys

breman1972 · 18 Jan 2010 at 20:29

Sorry what?

Better still why would you need to know this?

UltimateBadger · 18 Jan 2010 at 20:29

Found this...

since this function is its own inverse, it is symmetric to the line y = x?

http://answers.yahoo.com/question/index?qid=20090828214209AAspqjv

Haven't done this shizzle for years so I may be way off the mark!

bmi92 · 18 Jan 2010 at 20:32

breman1972 said:
Sorry what?

Better still why would you need to know this?

Is it that you don't understand my layout, or is it that you didn't do A-level math?

Ricochet J · 18 Jan 2010 at 20:32

breman1972 said:
Better still why would you need to know this?

Many applications:
- Calculate the exact surafce area of a F1 car
- Calculate the drag coeff on an aeroplane
- Estimate profit and loss of a company for the next few years

I could go on. Calculus is an important tool.

OP - Try y=x-1.

Jamesdavid3 · 18 Jan 2010 at 20:34

Seriously. when would you EVER need to do something like this in real life situations...

forget about it to be honest, just write on the test paper... I dont really care, im never going to use this in my entire life.

Ricochet J · 18 Jan 2010 at 20:36

Jamesdavid3 said:
Seriously. when would you EVER need to do something like this in real life situations...

What do you do for a living?

bmi92 · 18 Jan 2010 at 20:37

Jamesdavid3 said:
Seriously. when would you EVER need to do something like this in real life situations...

forget about it to be honest, just write on the test paper... I dont really care, im never going to use this in my entire life.

I don't really care when I'm going to use this exact application fo calculus to be honest. I just want to know how to do this question so that I can attain the maximum amount of marks avaliable in my exam, go on to study Math at university and then learn about the applications of calculus in a specific area and contribute to that area of society. Be it economics or aeronautical engineering

P.s read up for a list of applications.

Trifid · 18 Jan 2010 at 20:37

Jamesdavid3 said:
Seriously. when would you EVER need to do something like this in real life situations...

forget about it to be honest, just write on the test paper... I dont really care, im never going to use this in my entire life.

breman1972 said:
Sorry what?

Better still why would you need to know this?

Wow, great attitude you guys have.

I can't remember much from A level maths, sorry. Look forward to having a refresher though.

bmi92 · 18 Jan 2010 at 20:38

Ricochet J said:
Many applications:
- Calculate the exact surafce area of a F1 car
- Calculate the drag coeff on an aeroplane
- Estimate profit and loss of a company for the next few years

I could go on. Calculus is an important tool.

OP - Try y=x-1.

Thanks

Jasebta · 18 Jan 2010 at 20:38

You'd NEED to do something like this to pass A-level maths, for a start. I'm in the same boat as OP with C3 on Wednesday, and am bricking it as maths definitely isn't my strongest subject.

"andy" · 18 Jan 2010 at 20:39

Jamesdavid3 said:
Seriously. when would you EVER need to do something like this in real life situations...

you dont ever need it. but its important to know the basics behind it before you go off letting computers do it all for you.

it seperates the clever from the not so clever too. otherwise everyone would be engineers/scientists sat behind a computer that works out all the maths for them

Jamesdavid3 · 18 Jan 2010 at 20:42

"we have computers, use them...."

quote from myself.

Were in the 21st century now, you lot seem to be going back in time rather than forward, we have computers, use them.

Ricochet J · 18 Jan 2010 at 20:43

Jamesdavid3 said:
"we have computers, use them...."

quote from myself.

Were in the 21st century now, you lot seem to be going back in time rather than forward, we have computers, use them.

There are so many things wrong with what you just said I think I'll quote you so everyone can read your comment and laugh.

Jasebta · 18 Jan 2010 at 20:43

Jamesdavid3 said:
"we have computers, use them...."

quote from myself.

Were in the 21st century now, you lot seem to be going back in time rather than forward, we have computers, use them.

Tell that to the people that make the exams.

skippy2421 · 18 Jan 2010 at 20:49

am i correct in thinking for part (i) you actually mean F(x)=(x+1)/(x-1) because if so part (i) is easy and i'll explain it to ya if not aint got a clue

bmi92 · 18 Jan 2010 at 20:50

Yeah that's what I meant

jr1104 · 18 Jan 2010 at 20:51

Jamesdavid3 said:
"we have computers, use them...."

quote from myself.

Were in the 21st century now, you lot seem to be going back in time rather than forward, we have computers, use them.

You need to understand that the user still needs to understand and know how to use the methods that the computer is using. Often when doing complex mathematical modelling, you have to write the program yourself, and have an idea of what the answer should be. I've just finished writing a MATLAB script modelling the take-off of a Saturn V, and even though I didnt actually do any calculus myself, I had to understand how to do 3rd order differentation.

Lightnix · 18 Jan 2010 at 20:52

Jamesdavid3 said:
"we have computers, use them...."

quote from myself.

Were in the 21st century now, you lot seem to be going back in time rather than forward, we have computers, use them.

Never mind that somebody who has to know this sort of stuff has to engineer and program these computers.

Biohazard · 18 Jan 2010 at 20:53

Jamesdavid3 said:
"we have computers, use them...."

quote from myself.

Were in the 21st century now, you lot seem to be going back in time rather than forward, we have computers, use them.

you go girl