One part of the formation of a band has eight rows with five band members per row. The other part has four rows with seven members in each row.

Step-by-step explanation:

The line of symmetry is halfway between the zeros, so is found at ...

  x = (3 -1)/2 = 1

Part 1

If point (1-p, y) is on the graph, so is the point that is its reflection in the line of symmetry: (2 -(1-p), y) = (1+p, y).

__

Part 2

If x=a is the line of symmetry, a=1, since x=1 is the line of symmetry as found above.

_____

Comment on midpoint & line of symmetry

If M is the midpoint between A and B, then ...

  M = (A+B)/2

  B = 2M -A . . . . solve for B

The reflection of a point (x, y) in the line x=a will be (2a-x, y). That is where the "2" comes from in the equation used in part 1.