\((1)\)计算:\( \sqrt{16} =\)_____.
\((2)\)化简:\( \dfrac{x}{x+3}+ \dfrac{3}{x+3} =\)_______.
\((3)\)如图把一张长方形纸片\(ABCD\)沿\(EF\)折叠后,\(ED\)交\(BC\)于点\(G\),点\(D\)、\(C\)分别落在\(D′\)、\(C′\)位置上\(.\)若\(∠EFG=50^{\circ}\),那么\(∠EGB=\)_____\({\,\!}^{\circ}\).
\((4)\)在如图所示的电路中,随机闭合开关\(S\)\({\,\!}_{1}\)
,\(S\)\({\,\!}_{2}\)
,\(S\)\({\,\!}_{3}\)
中的两个,能让灯泡\(L\)\({\,\!}_{1}\)
发光的概率是_____. \((5)\)如图,平行于\(x\)轴的直线\(AC\)分别交函数\(y_{1}=x^{2}(x\geqslant 0)\)与\(y_{2}= \dfrac{{x}^{2}}{3} (x\geqslant 0)\)的图象于\(B\)、\(C\)两点,过点\(C\)作\(y\)轴的平行线交\(y_{1}\)的图象于点\(D\),直线\(DE/\!/AC\),交\(y_{2}\)的图象于点\(E\),则\( \dfrac{DE}{AB} =\)_________.
\((6)\)矩形\(ABCD\)中,\(AB=4\),\(AD=3\),\(P\),\(Q\)是对角线\(BD\)上不重合的两点,点\(P\)关于直线\(AD\),\(AB\)的对称点分别是点\(E\)、\(F\),点\(Q\)关于直线\(BC\)、\(CD\)的对称点分别是点\(G\)、\(H.\)若由点\(E\)、\(F\)、\(G\)、\(H\)构成的四边形恰好为菱形,则\(PQ\)的长为_____.