point of inflexion question (1 Viewer)

[Halo189]

poi of y=(1+x^2)/(1-x^2)

ans: (-1/ sqr 3, 1/2) and (1/sqr 3. 1/2)

st pt is (0,1) <----- I got this cant seem to get the poi though...

thx

 

[InteGrand]

Have you managed to differentiate the function twice? Set the second derivative to 0 and solve for x to find (possible) points of inflexion (still need to test them to make sure concavity changes about these points, or justify it some other way).

 

[Halo189]

yeah I have but still not getting the answer...
it doesn't end up as a quadratic just another type of equation

 

[porcupinetree]

Are you sure that the function isn't (1 - x^2)/(1 + x^2)? The function you wrote has no points of inflection, and the function I wrote has the correct points of inflection.

 

[InteGrand]

Are you sure that the function isn't (1 - x^2)/(1 + x^2)? The function you wrote has no points of inflection, and the function I wrote has the correct points of inflection.

Yep, that's probably right, since the inflection points the original poster wrote don't even lie on the original curve, but they do on the one for the function you wrote.

 

[Lithone]

Yep, that's probably right, since the inflection points the original poster wrote don't even lie on the original curve, but they do on the one for the function you wrote.

Brackets are important...

 

[InteGrand]

Brackets are important...

What do you mean?

 

[Halo189]

lol sorry yeah it is I did a typo its (1-x^2)/1+x^2)
sooooooooooorrrrrrrrryyyyyyyyyyyy

 

[Halo189]

so how did you get it?

 

[Halo189]

if you could just the second derivative part cause I got the stpt part thx

 

[FrankXie]

what have you got for the second derivative?

 

[Halo189]

what have you got for the second derivative?

x=1/2

 

[FrankXie]

no. i meant your y''=?

 

[Halo189]

no. i meant your y''=?

y''=(-4(1+x^2)^2-2x.2(1+x^2).4x)/(1+x^2)^4

 

[Halo189]

probs y'' is wrong...

 

[FrankXie]

thats good, but can you simplify a little bit, because you are going to solve y''=0

 

[FrankXie]

probs y'' is wrong...

oh yes the second minus should be plus

 

[Halo189]

lol thx I got it
I did a silly mistake whilst simplifying XD