How can plugging 1 and -1 into x^2-1/x^2 give me (1,2) and (-1,-2)?

[awesomest47]

I've been following along a derivative problem from the answers in my calc homework and so far, my work has been a match. The problem asks for horizontal pairs of three tangent lines for the derivative x^2-1/x^2. I set this equal to zero and got that x could be 1 or -1 but when I plug either of these into my function to get an ordered pair, I get (-1, 0) and (1,0) but the answers key says it should be (1,2) and (-1,-2.) Am I doing something wrong or is it the answer key?? Thanks for all the help everyone gives on this website!

 

[Deleted member 4993]

I've been following along a derivative problem from the answers in my calc homework and so far, my work has been a match. The problem asks for horizontal pairs of three tangent lines for the derivative x^2-1/x^2. I set this equal to zero and got that x could be 1 or -1 but when I plug either of these into my function to get an ordered pair, I get (-1, 0) and (1,0) but the answers key says it should be (1,2) and (-1,-2.) Am I doing something wrong or is it the answer key?? Thanks for all the help everyone gives on this website!

There could be many things wrong - on either side! What was the original problem?

 

[awesomest47]

There could be many things wrong - on either side! What was the original problem?

Sorry for the inconvenience! I just looked at the problem again and I think my mistake was not plugging the answers I received from setting the derivative to zero into the original function (x^2+1/x). I plugged it into the derivative instead! Thank you for the help though!