The graph of a quadratic polynomial is U-shaped or an inverted U, assuming it is of the form ax^2+bx+c. When the zeroes are real, the graph cuts the x axis in two places. If the zeroes are equal, so that the polynomial is a perfect square, it touches the x axis but doesn't cut it. Because of the shape the only way the polynomial is if it has the form x=ay^2+by+c. This is a parabola on its side.
Example: y=3x^2+2x-1 is a typical parabola.
