How do I show kids how to find all the zeros for polynomials degree 4 and bigger.

For examples:

r(x) = x^{5}-11x^{3}-7x^{2}+77 = (x^{2}-11)(x^{3}-7) and s(x) = x^{4}-121 = (x^{2}-11)(x^{2}+11)

Also am I correct when I say that the following are irreducible?

f(x) = x^{2}-11

g(x) = x^{3}-7

h(x) = x^{4}-5