The points of intersection of the graphs of four functions given by the formulas $y=k x+b, y=k x-b, y=m x+b$ and $y=$ $m x-b$, are the vertices of a quadrilateral. Find the coordinates of the point of intersection of its diagonals.
From the equations, it is clear that the graphs of these linear functions are two pairs of parallel lines. Therefore, the points of intersection of the graphs are the vertices of a parallelogram. Two opposite vertices of this parallelogram are $M(0, b)$ and $N(0,-b)$. Since the diagonals of a parallelogram bisect each other, the required point is the midpoint of segment $M N$, which is the point $(0,0)$.

## Answer

$(0,0)$.