Parabolas Here is a simple parabola, or quadratic function. Its equation is   y = x2 - 3 There is a portion of this graph that is negative. It looks like everything on the graph from x values of about -1.7 to +1.7 When we apply the absolute value bars to this function, the curved part of the parabola that is below the X axis will reflect upwards. Have a look below. On the right is the graph of the function   y = |x2 - 3| All of the negative values of this function have become positive. The portion that was below the X axis has been reflected above the axis. ... now let's look at a cubic function Main Page