MHB Can you prove this fraction problem with mean proportion?

[kuheli]

if b is the mean proportion between a and c ; prove that

(a^2 - b^2 + c^2) / (a^-2 - b^-2 + c^-2) = b^4

 

[Petrus]

Re: please help with this fraction problem

if b is the mean proportion between a and c ; prove that

(a^2 - b^2 + c^2) / (a^-2 - b^-2 + c^-2) = b^4

Hello,
Do you got any progress?
do you know what they mean with "b is the mean proportion between a and c"

Spoiler

$$b^2=ac$$ put that on left side what do you got?

Regards,
$$|\pi\rangle$$

 

[kuheli]

ya i got it .. thanks a lot :)