7.
\((1) \overset{⇀}{a} =(\)\(x\)\(-1\),\(y\)\()\),\( \overset{⇀}{b} =(1,2)\),且\(\overrightarrow{a}\bot \overrightarrow{b}\),则当\(x > 0,y > 0\)时,\(\dfrac{1}{x}+\dfrac{1}{y}\)的最小值为 ______.
\((2)\)向量\(\overrightarrow{a}=\left( 2,3 \right)\)在\(\overrightarrow{b}=\left( -4,7 \right)\)上的投影是 ______.
\((3)\)若等比数列\(\left\{ {{a}_{n}} \right\}\)满足\({{a}_{1}}+{{a}_{3}}=20\),\({{a}_{2}}+{{a}_{4}}=40\),则公比\(q=\) ______\(..\)
\((4)\)已知\(m,n,p\)表示不重合的三条直线,表示不重合的三个平面\(.\)给出以下四个命题
\(①\)若\(m⊥p\),\(m/\!/n\)则\(n⊥p\)
\(②\)若\(m/\!/β\),\(n/\!/β\),\(m⊂ α\),\(n⊂ α\),则\(α/\!/β③\)若\(α⊥γ\),\(β⊥γ\),\(α∩β=m\),则\(m⊥γ\)
\(④\)若\(α/\!/β\),\(m⊂ α\),\(n⊂ β\),则\(m/\!/n\)
其中正确命题的序号是 \((\)把所有正确命题的序号都写上\()\)