Find the interval in which y=x(x- 1)(x-2) is positive: (0, 1) u (2, +∞).

When looking for monotonous intervals, we should pay attention to continuity, so we generally use and/or.

When calculating the range of values, do not emphasize continuity, and then use u.

Pay special attention to this when studying derivatives. At this time, the derivative determines monotonicity. When judging whether the derivative is greater than zero or less than zero, the result should be U, but when the derivative is finished, and/or will be used.