If you are asked to write down , for example, a polynominal of degree 2 that has 2 and 3 as its zeros, you will find;

f(x) = (x-2)(x-3)

by substituting either x=2 or x=3, it's clear this satisfies the question.

Similarly,....

+ if an polynominal f(x)=0 <whose coefficient is all real> has an complex root, x = a+bi, (a and b are real), we can say...