Write one quadratic polynomial that has one zero.

A quadratic polynomial can be written in the form of:

f(x) = a(x - r)(x - s)

Where 'a' is a non-zero constant and 'r' and 's' are the zeros of the polynomial.

To have one zero, we can set 'r' and 's' as the same value. Let's assume that the zero is 'r'. Therefore, the quadratic polynomial with one zero can be written as:

f(x) = a(x - r)(x - r)

Simplifying this expression:

f(x) = a(x - r)^2

This quadratic polynomial has one zero at 'r'.