The document provides a formula and examples for finding the square of a trinomial. The formula is: F2 + M2 + L2 + 2FM + 2FL + 2ML, where F is the first term, M is the middle term, L is the last term, and the other terms represent twice the product of the terms. It then works through four examples applying the formula to find the square of trinomials such as (a + b + c)2, (x + y - 3)2, (x - 2y - 1)2, and (2a - b + b2)2.