The slope is -10, I used a graph for this.
To
understand this picture 2 cones that are stacked one on top of
another. A double-napped cone is created when a generator is rotated
about a fixed vertical axis. A line is created when the cone is cut
by a plane containing the generator. Please see the attachment to
help you understand this.
I
hope this helps, Regards.
A. -1 Because you would divide 3x and -6 by 2.