Object of 1. formula: the formula matches a constant term with quadratic coefficient of 1 (meaning: 1. This formula matches the constant term 2. The quadratic coefficient is 1). 2. Preparation of formula: First, move the constant term to the right. 3. Formula method: the two sides of the equation are matched with the square of half the coefficient of the first term. 4. If the coefficient of quadratic term is not 1, it is very simple. If both sides of the equation are divided by this coefficient, the quadratic coefficient will be converted into 1, and the formula will be fine. Like x? 0? 5-8X-9=0, first shift the constant term to the right, x? 0? 5-8X=9, and the formula of half the coefficient of the first term on both sides of the equation is 16. x？ 0? 5-8X+ 16=9+ 16，(X-4)？ 0? 5 = 25, the formula is successful. Like 3X? 0? 5-8X-2=0, first shift the constant term to the right, 3X? 0? 5-8X=2 and the coefficient of ∵ quadratic term is not 1. Then, if both sides of the equation are divided by 3, the coefficient of the quadratic term becomes 1, x? 0? 5-8/3 X=2/3, and then both sides are squared by half of the coefficient of the first term, 16/9, and the left side of the equation is completely squared. Remember those four sentences, and the collocation method will not beat you!