If 1 is a zero of the polynomial P(x), then:
P(1) = 1
P(1)=0
P(1) = 1 and P(1) = 0
P(1) = 2
A real number k is said to be a zero of a polynomial P(x) if P(k) = 0. Therefore, P(1) = 0. P(2) - P(1) = P(2) - 0 = P(2)