prep2 DS 坐标系题，请教NN

In the xy-coordinate plane, line m and line k intersect at the point (4, 3).  Is the product of their slopes negative?

 要用点斜式列方程计算吗？

答案：C

(1)  The product of the x-intercepts of lines m and k is positive.

(2)  The product of the y-intercepts of lines m and k is negative.

谢谢各位大侠

graph....