Question

已知抛物线y=x^2-(k+3)x+2k-1···急!

Answer 1

设A（x1,0）,B(x2,0)

由已知条件可得：C((k+3)/2,m)

将点C坐标代入方程得:

[(k+3)/2]^2-(k+3)*(k+3)/2+2k-1=m

化简得：(k+3)^2-8k+4=-4m

AB^2=(x2-x1)^2=(x1+x2)^2-4x1x2

=(k+3)^2-4(2k-1)=(k+3)^2-8k+4=-4m

所以

AB^2/m=-4m/m=-4