這一次的重難點筆記，我們將注意力放在較為基礎(chǔ)，但卻又非常重要的二次方程的解法上。在同學們八年級和九年級的學習中，我們已經(jīng)逐漸了解和掌握了因式分解法求二次方程解的一般步驟，講方程分解為(x-a)(x-b)=0的形式，然后發(fā)現(xiàn)x可以等于a或者b。

但是，隨著同學們的習題量增多，大家發(fā)現(xiàn)，我們的數(shù)學中存在著很大一部分的二次方程，它們并不可以用因式分解法找出答案，因為他們的解往往以根式(無理數(shù))的形式存在，所以，這就需要我們開發(fā)新的方法去求解更加普遍和一般的二次函數(shù)。

This time, we will focus on the more basic but very important solution of quadratic equations. In the eighth and ninth grades of the students, we have gradually understood and mastered the general steps to find the solution of a quadratic equation by factoring, decomposing the equation into the form of (x-a)(x-b)=0, and then finding x Can be equal to a or b.

However, with the increase in the number of exercises for students, we found that there are a large part of quadratic equations in our mathematics, and they cannot be solved by factoring, and their solutions often appear in the form of irrational numbers . Therefore, this requires us to develop new methods to solve more general quadratic functions.

用完成平方的方法解一元二次方程可歸納成如下步驟：

（1）移項將二次項、一次項保留在方程的左邊，把常數(shù)“孤立”在方程的右邊

（2）化二次項系數(shù)為1兩邊同時除以二次項的系數(shù)

（3）配方兩邊同時加上一次項系數(shù)一半的平方

（4）兩邊開平方

（5）寫出方程的解，解線性方程

具體例題如下：

Solving the quadratic equation in one variable by the method of completing the square can be summarized into the following steps:

(1) Shifting the term keeps the quadratic term and the primary term on the left side of the equation, and "isolates" the constant on the right side of the equation

(2) Convert the coefficient of the quadratic term to 1 and divide both sides by the coefficient of the quadratic term

(3) Add the square of half of the coefficient of the first-order term on both sides of the formula at the same time

(4) Square root on both sides

(5) Write the solution of the equation and solve the linear equation

二次方程作為數(shù)學的基礎(chǔ)，希望大家要勤聯(lián)系，少犯錯。我也希望以上的總結(jié)能夠?qū)Υ蠹仪蠼舛畏匠逃袔椭?/p>