2、① 6,3/2,3/8,0,3/8,3/2,6;

-6,-2/3,-3/8,0,-3/8,-3/2,-6

② Sketch

3 、( 1)y = 2x？ The point (1, 2) is on a parabola.

(2) The opening is upward, the vertex coordinate is (0,0), the symmetry axis is the Y axis, and the parabola is above the X axis.

4. Omission

5、y = - 1/9x？

6 、( 1)y = -3/50x？

(2) Substitute x = 5 into y = -3/50x? , y =-1.5, and the water level reached the warning line after 22.5 hours.