If the polynomial x + ax + 169 is the square of a polynomial, find the value of A It's x ^ 2 + ax + 169,?

If the polynomial x + ax + 169 is the square of a polynomial, find the value of A It's x ^ 2 + ax + 169,?

It should be: x ^ 2 + ax + 169,
169=13^2
Then: a = ± 2 * 13 = ± 26