We have a mathematical equation in the form of a×a+a=306. This equation is a quadratic equation, and our goal is to find the value of A. In this equation, the unknown is A. According to the topic, we can establish the following equation a×a+a=306. Using mathematical symbols, we can express it as: A 2+A = 306. Now we need to solve this equation and find the value of a, and the calculation result is [{a:-18}, {a: 17}], so the value of a is-18.