To find the value needed to create a perfect square trinomial, first take the coefficient in front of the x term (not the x2 term). The coefficient in front of the x term for this problem is 8. Now, divide that number by 2. 8 divided by 2 gives 4. We take that answer and square it. 4^2 = 16. 16 is the final answer, so x2+8x+16 is a perfect square trinomial. No matter what the coefficient is in front of the x term, if you always divide it by 2 and then square that answer, you will get the value that creates a perfect square trinomial.