若集合A={x|x2+(k-3)x+k+5=0,x∈R},A∩R+≠Φ,则实数k的取值范围为_.
问题描述:
若集合A={x|x2+(k-3)x+k+5=0,x∈R},A∩R+≠Φ,则实数k的取值范围为______.
答
由题意知:方程x2+(k-3)x+k+5=0必有正根,从x2+(k-3)x+k+5=0中得
-k=
= x+1+
x2−3x+5 x+1
−5≥1,∴k≤-19 x+1
故填 (-∞,-1].