How do you graph y^2(x^2-1)=1 ?

1 Answer
Jan 13, 2017

See explanation...

Explanation:

Interesting!

Let's start by considering:

y(x^2-1) = 1

Dividing both sides by x^2-1 we get:

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

This has vertical asymptotes at x=+-1 and a local maximum at x=0, where y = -1.

It is only positive when abs(x) > 1

It has a horizontal asymptote y = 0 since 1/(x^2-1) -> 0 as x->+-oo.

So it looks like this...
graph{1/(x^2-1) [-10, 10, -5, 5]}

Going back to our original equation, we can divide both sides by x^2-1 to get:

y^2 = 1/(x^2-1)

and hence:

y = +-sqrt(1/(x^2-1))

This does not describe a function, but has a graph which will be symmetrical about the x axis.

Considering just the positive values, note that square roots are monotonically increasing, approaching vertical for small values of the radicand...
graph{(y^2-x) = 0 [-10, 10, -5, 5]}

So combined with the function 1/(x^2-1) this results in a graph which is less 'steep' near the vertical asymptotes, undefined for abs(x) <= 1 and slower to approach the asymptote y=0, with a reflected copy...
graph{y^2(x^2-1)=1 [-10, 10, -5, 5]}