Sketching Quadratic Curve Given a quadratic curve, you will need to let x=0 and then y=0, and to find the required coordinates of points the graph intercept with the x-axis and y-axis. By looking at the cooefficient of the x-square term, a>0, the curve is opened upward (smiley face), when a<0, the curve is opened downward (sad face). Find the Mid-point of the x-intercept, substituding x value into equation, you will get the coordinates of the minimum or maximum point of the graph.