共50条信息
设\(F\)为抛物线\(C:{{y}^{2}}{=}3x\)的焦点,过\(F\)且倾斜角为\(30{}^\circ \)的直线交\(C\)于\(A\),\(B\)两点,则\(\left| AB \right|=\)
已知抛物线\(C:{{y}^{2}}=4x\),经过焦点\(F\)的直线\(l\)与抛物线\(C\)交于\(A,B\)两点,\(A\)在\(x\)轴的上方,\(Q\left( -1,0 \right)\)\(.\)若以\(QF\)为直径的圆经过点\(B\),则\(\left| AF \right|-\left| BF \right|=\)
已知抛物线\(C\):\({{y}^{2}}=4x\)的焦点为\(F\) ,准线为\(l\) ,若射线\(y=2\left(x-1\right)\left(x\leqslant 1\right) \)与\(C\),\(l\)分别交于\(P\),\(Q\)两点,则\(\dfrac{\left| PQ \right|}{\left| PF \right|} =(\) \()\)
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