已知关于x的方程x2﹣2(k﹣3)x+k2﹣4k﹣1=0. (1)若这个方程有实数

已知关于x的方程x22k3x+k24k1=0

1)若这个方程有实数根,求k的取值范围;

2)若以方程x22k3x+k24k1=0的两个根为横坐标、纵坐标的点恰在反比例函数的图象上,求满足条件的m的最小值.

答案

【考点】根的判别式;根与系数的关系;反比例函数图象上点的坐标特征.

【专题】计算题.

【分析】1)根据的意义得到4k324k24k10,然后解不等式得到k5

2)设方程的两根分别为x1x2,根据根与系数的关系得到x1x2=k24k1,再根据反比例函数图象上点的坐标特点得m=x1x2=k24k1,配方得到m=k225,再根据非负数的性质得到(k2250,于是m的最小值为﹣5

【解答】解:(1)根据题意得4k324k24k10,解得k5

所以k的取值范围为k5

2)设方程的两根分别为x1x2

x1x2=k24k1

方程两个根为横坐标、纵坐标的点恰在反比例函数的图象上,

m=x1x2=k24k1=k225

k220

k2255

m的最小值为﹣5

【点评】本题考查了一元二次方程ax2+bx+c=0a0)的根的判别式=b24ac:当0,方程有两个不相等的实数根;当=0,方程有两个相等的实数根;当0,方程没有实数根.也考查了一元二次方程的根与系数的关系以及反比例函数图象上点的坐标特点.

 

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