2019年中考数学专题训练-一元二次方程系数与根的关系(含解析).docx

《2019年中考数学专题训练-一元二次方程系数与根的关系(含解析).docx》由会员上传分享，免费在线阅读，更多相关内容在教育资源-天天文库。

1、2019中考数学专题训练-一元二次方程系数与根的关系（含解析）一、单选题1.若、是一元二次方程的两根，则的值是（   ）A. -2                                           B. 2                                           C. 3                                           D. 12.一元二次方程x2+3x﹣a=0的一个根为﹣1，则另一个根为（  ）A. ﹣2                            

2、             B. 2                                         C. 4                                         D. ﹣33.已知方程x2-5x+2=0的两个解分别为m，n，则m+n-mn的值是（　　）A. -7                                          B. -3                                          C. 7                            

3、              D. 34.若关于x一元二次方程x2﹣x﹣m+2=0的两根x1，x2满足（x1﹣1）（x2﹣1）=﹣1，则m的值为（　　）A. 3                                          B. -3                                          C. 2                                          D. -25.下列方程中：①x2-2x-1=0，②2x2-7x+2=0，③x2-x+1=0两根互为倒数有（  ）A.0个

4、B.1个C.2个D.3个6.设x1，x2是一元二次方程-2x-3=0的两根，则 =（　　）A. 6                                          B. 8                                          C. 10                                          D. 127.一元二次方程x2＋x－2＝0的两根之积是(  )A. －1                                         B. －2        

5、                                 C. 1                                         D. 28.方程x2+2x-4=0的两根为x1，x2，则x1+x2的值为（　　）A. 2                                        B. －2                                        C.                                         D. －9.若矩形的长和宽是方程x2﹣7x+12

6、=0的两根，则矩形的对角线之和为（  ）A. 5                                           B. 7                                           C. 8                                           D. 1010.如果a，b是一元二次方程x2﹣2x﹣4=0的两个根，那么a3b﹣2a2b的值为（　　）A. -8                                         B. 8            

7、                             C. -16                                         D. 1611.如果是一元二次方程的两个实数根，那么的值是（   ）A.                                           B.                                           C.                                           D. 二、填空题12.设x1、x2是方程x2-4x+3=0

8、的两根，则x1+x2=________ .13.定义新运算“*”，规则：a*b=，如1*2=2，*．若x2+x﹣1=0的两根为x1，x2，则x1*x2=______