I remember this problem from an old video of yours on your main channel. "Someone" in the comments gave an explanation for why f(x) = 1/x and f(x) = -1/x are not the only solution.
An example of a function that solves the equation but is neither f(x) = 1/x nor f(x) = -1/x *[Disclaimer: it is copy-pasted from the old video]* Let f(x) = -1/x if and only if x = -1, 1/2, 2, and f(x) = 1/x otherwise. This is a piecewise function that satisfies the functional equation, but is not equal to f(x) = -1/x for all x, and is not equal to f(x) = 1/x for all x.
Another example *[Also copy-pasted]* Here, another example. Let f(x) = 1/x if and only if x = e, 1/(1 - e), 1 - 1/e, π, 1/(1 - π), 1 - 1/π, and f(x) = -1/x otherwise. Again, this satisfies the equation, yet is different from all three of the solutions I have mentioned.
It turned out that the person I am mentioning wrote his explanation in a reply, not a comment. Check under the comment of @******* YT doesn't want me to mention usernames. I already have tried twice and both replies got shadowbanned.
As a matter of fact all functions that are either 1/x or 1/-x for any specific value of x different from 1 and 0(a domain restriction imposed by the initial problem but completely ignored throughout the solution ) are also solutions.
Everytime I included the link to Syber's old video or the username of the person I want you to read the replies under his comment, YT decides to obliterate my reply.
Syber has already posted this problem in an old video on his main channel. Someone in the replies to @***** gave an explanation for why those aren't the only solutions. Go check it out!
@@TH-cam_username_not_found I found the older video on the other channel. Thanks for pointing me to that place and the comments regarding piecewise definitions of f(x).
Immediately I noticed that they're both reciprocals, so f(x)=1/x
Good equation
I remember this problem from an old video of yours on your main channel. "Someone" in the comments gave an explanation for why f(x) = 1/x and f(x) = -1/x are not the only solution.
An example of a function that solves the equation but is neither f(x) = 1/x nor
f(x) = -1/x *[Disclaimer: it is copy-pasted from the old video]*
Let f(x) = -1/x if and only if x = -1, 1/2, 2, and f(x) = 1/x otherwise. This is a piecewise function that satisfies the functional equation, but is not equal to f(x) = -1/x for all x, and is not equal to f(x) = 1/x for all x.
Another example *[Also copy-pasted]*
Here, another example. Let f(x) = 1/x if and only if x = e, 1/(1 - e), 1 - 1/e, π, 1/(1 - π), 1 - 1/π, and f(x) = -1/x otherwise. Again, this satisfies the equation, yet is different from all three of the solutions I have mentioned.
It turned out that the person I am mentioning wrote his explanation in a reply, not a comment. Check under the comment of @*******
YT doesn't want me to mention usernames. I already have tried twice and both replies got shadowbanned.
As a matter of fact all functions that are either 1/x or 1/-x for any specific value of x different from 1 and 0(a domain restriction imposed by the initial problem but completely ignored throughout the solution ) are also solutions.
Example: f(x) = 1 / x for x rational and -1/x otherwise defined for x not equal to 0 or 1 satisfies this property.
Multiply (1) and (3) equations first and replace the part of product by the expression of (2) equation. You'll get the same result but faster.
😊😊😊👍👍👍
Suppose y=1/(1-x) then equation one becomes f(x)f(y)=1/(yx). This suggests f(x)=1/x. Apply in equation one: it fits! Solved.
... and of course f(x)=-1/x
f(x) = ±1 / x was easy to guess but hard to proof that it is the only solution.
My replies to you keep getting deleted. ☹
Everytime I included the link to Syber's old video or the username of the person I want you to read the replies under his comment, YT decides to obliterate my reply.
Syber has already posted this problem in an old video on his main channel. Someone in the replies to @***** gave an explanation for why those aren't the only solutions. Go check it out!
Just check my comment to this video and the replies under it.
@@TH-cam_username_not_found I found the older video on the other channel. Thanks for pointing me to that place and the comments regarding piecewise definitions of f(x).
(1)(3)/(2)
(f(x))^2 = 1/x^2
f(x) = +- 1/x