Sketch the following graphs, indicating the points where they cross the x-axis:

a. y = x(x – 2)(x + 2)

b. y = |x(x – 2)(x + 2)|

c. y = 3(2x – 1)(x + 1)(x + 3)

d. y = |3(2x – 1)(x + 1)(x + 3)|