7.
如图,直角坐标系\(xOy\)中,直线\(l_{1}\):\(y=tx-t(t\neq 0)\)分别与\(x\)轴、\(y\)轴交于\(A\),\(B\)两点,与双曲线\(l_{2}\):\(y=\dfrac{k}{x}(k\neq 0)\)交于点\(D(2,2).\)点\(B\),\(C\)关于\(x\)轴对称,连接\(AC\),将\(Rt\triangle AOC\)沿\(AD\)方向平移,使点\(A\)移动到点\(D\),得到\(Rt\triangle DEF\).
\((1)k\)的值是________,点\(A\)的坐标是________;
\((2)\)点\(F\)是否在\(l_{2}\)上,并验证你的结论;
\((3)\)在\(ED\)的延长线上取一点,\(M(4,2)\),过点\(M\)作\(MN/\!/y\)轴,交\(l_{2}\)于点\(N\),连接\(ND\),求直线\(ND\)的解析式;
\((4)\)直接写出线段\(AC\)扫过的面积.