Binkov A. D:

After the lesson, the graph of the function $y=k / x$ and five lines parallel to the line $y=k x$ ( $k \neq 0$ ) remained on the board. Find the product of the abscissas of all ten intersection points.
A line parallel to the line $y=k x$ has the equation $y=k x+b$. The abscissas of the points of its intersection with the hyperbola are both roots of the equation $k / x=k x+b \quad \Leftrightarrow \quad k x^{2}+b x-k=0$. The product of the roots of this equation is -1. Multiplying five such products, we get the answer.

## Answer

$-1$.