设函数y=x^2-(k+1)x-4(k+5),与x - 知识问答

0k" +18k+81>0k≠9x"-(k+1)x-4(k+" property="og:description"/> 设函数y=x^2-(k+1)x-4(k+5),与x - 知识问答 0k" +18k+81>0k≠9x"-(k+1)x-4(k+"/>

设函数y=x^2-(k+1)x-4(k+5),与x轴交A、B,OA:OB=1:4,则k=?

4个回答

y=x^2-(k+1)x-4(k+5),与x轴有两个交点
则(k+1)" +16(k+5)>0
k" +18k+81>0
k≠9
x"-(k+1)x-4(k+5) = [x-(k+5)][x+4] = 0
x = -4,x = k+5
由图可知K+5〉0
|-4|：(K+5) = 1：4时
k = 11

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