P1 = x
P2 = x^3
P3 = 4
P4 = -3x
Q  = 0

Q1 = P1 + P2
Q1 = x^3 + x

Q2 = Q1 + P3
Q2 = x^3 + x + 4

Q  = Q1 + Q2
Q  = 2x^3 + 2x + 4

Q  = Q + P1
Q  = 2x^3 + 3x + 4

Q  = Q + P4
Q  = 2x^3 + 4

Q  = Q + P4 + Q1
Q  = 3x^3 -2x + 4

Q3 = Q2 - Q1
Q3 = 4

Q3 = Q2 - Q2
Q3 = 0