For x-values up to -1, the first test function is true (returns a value of 1) but the second test function is false (returns a value of 0). For these values of x, the Y1 expression is being divided by one and the line is graphed. The Y2 expression is being divided by zero, which is undefined, so the parabola is not graphed. For values of x greater than -1, the opposite is true.

Notice that the two pieces do not meet, so this graph is discontinuous at x = -1.