There is two possible conic section that can be formed when the plane intersects the vertical axis, a circle, and an ellipse. Cutting one nappe of double napped cone perpendicular to the vertical axis means the cut is straight across the cone making a right angle. The conic section formed would be a circle.
He pays 119.93$ but including tax he pays 128.92$ With the tax being 8.99$
2+4a=-10
First, subtract 2 from both sides.
4a=-12
Then divide 4 from both sides.
a=-3
hope it helps!