Follow the method in Step 1 to determine if the fourth expression is a perfect square trinomial. The first term and the third term of the fourth trinomial, 4x^2 + 12x + 9, are perfect squares. 4x² = (2x)² 9 = (3)² Because the x-term is positive, if the trinomial is a perfect square, then it is the square of a binomial sum. Find the square of the binomial formed by the sum of the square roots of the perfect squares, (2x + 3)². You can use the distributive property to square the binomial. Or you can use the rule for squaring a binomial sum, (a + b)² = a² + 2ab + b², with a = 2x and b = 3. Compare the original trinomial to the square of the binomial.