1.根据根的定义,将根直接代入原方程求系数例1已知x=2是一元二次方程x~2+mx+2=0的一个解,则m的值是().A.-3 B.3 C.0 D.0或3分析:根据根的定义,把方程的解直接代入原方程,这是一种常用方法.解:把x=2代入原方程可得到一个关于m的一元一次方程,再求解.选A.2.直接求根,将其代入所求式子例2已知m是方程x~2-x-2=0的一个实数根, 1. According to the definition of the root, the root directly into the original equation to find the coefficient Example 1 Known x = 2 is a solution of the quadratic equation x ~ 2 + mx + 2 = 0, then the value of m is () .A. -3 B.3 C.0 D.0 or 3 Analysis: According to the definition of root, the solution of the equation is directly substituted into the original equation, which is a common method. Solution: Substituting x = 2 into the original equation yields a Choose A.2. Find the root directly and substitute it into the required subroutine. Example 2 It is known that m is a real root of the equation x ~ 2-x-2 = 0,