共50条信息
已知直线\(x-y+1=0\)与抛物线\(y=ax^{2}\)相切,则\(a=\)________.
过抛物线\(x\)\(=4\)\(y\)的焦点作直线交抛物线于\(A(\)\(x\)\({\,\!}_{1}\),\(y\)\({\,\!}_{1})\)和\(B(\)\(x\)\({\,\!}_{1}\),\(y\)\({\,\!}_{2})\)两点,若\(y\)\({\,\!}_{1}+\)\(y\)\({\,\!}_{2}=6\),则线段\(AB\)的长是__________\(.\)
已知抛物线\(C\):\(y\)\({\,\!}^{2}=8\)\(x\),\(O\)为坐标原点,直线\(x\)\(=\)\(m\)与抛物线\(C\)交于\(A\),\(B\)两点,若抛物线\(C\)的焦点\(F\)恰好为\(\triangle \)\(OAB\)的重心,则线段\(AF\)的长为________.
我国唐代诗人王维诗云:“明月松间照,清泉石上流”,这里明月和清泉,都是自然景物,没有变,形容词“明”对“清”,名词“月”对“泉”,词性不变,其余各词均如此\(.\)变化中的不变性质,在文学和数学中都广泛存在\(.\)比如我们利用几何画板软件作出抛物线\(C\):\(x^{2}=y\)的图象\((\)如图\()\),过交点\(F\)作直线\(l\)交\(C\)于\(A\)、\(B\)两点,过\(A\)、\(B\)分别作\(C\)的切线,两切线交于点\(P\),过点\(P\)作\(x\)轴的垂线交\(C\)于点\(N\),拖动点\(B\)在\(C\)上运动,会发现\(\left| \dfrac{NP}{NF}\right| \)是一个定值,该定值是 .
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