3.
已知函数\(y=x+ \dfrac {a}{x}\)有如下性质:如果常数\(a > 0\),那么该函数在\((0, \sqrt {a}]\)上是减函数,在\([ \sqrt {a},+∞)\)上是增函数.
\((\)Ⅰ\()\)若函数\(y=x+ \dfrac {2^{b}}{x}(x > 0)\)的值域为\([6,+∞)\),求实数\(b\)的值;
\((\)Ⅱ\()\)已知\(f(x)= \dfrac {4x^{2}-12x-3}{2x+1},x∈[0,1]\),求函数\(f(x)\)的单调区间和值域;
\((\)Ⅲ\()\)对于\((\)Ⅱ\()\)中的函数\(f(x)\)和函数\(g(x)=-x-2c\),若对任意\(x_{1}∈[0,1]\),总存在\(x_{2}∈[0,1]\),使得\(g(x_{2})=f(x_{1})\)成立,求实数\(c\)的值.