how solve the inequality $−1\leq \leq1$? How can we solve this equation graphically ? why we talk about the two hyperbole $\frac{1}{x}$ and $\frac{-1}{x}$ ?
I divided this equation on two sub-equations $$ xy\leq1$$ and  $$xy\geq-1$$.
For the first sub-equation  I have two cases when x is greater or not than zero. Also for the second I have two other equations depending if $x \geq0$ or not.
That said, I no longer know how to solve my system of 4 sub equations

The domain of the solutions is delimited by the two hyperbolas $xy=-1$ and $xy=1$ (each with two branches).
These partition the plane in five regions, one being a "cross" in the middle. As $(0,0)$ is a solution, the whole cross, including boundaries, is the solution set. (There cannot be solutions on the "other side" of a boundary.)
